The black screen of death.                  
See Dead PC tests here. (basics) Read this first.
Back screens symptoms can be boiled down to 2 things bad hardware (even batteries) and bad software. 
The PC can be locked up in Sleep mode , so do a forced power reset seen here.
A dead screen is first then BIOS screens 2nd. (in most cases if the screen is dead and the fans are dead, it is a power issue)
In  cases like this it is best to first get the BIOS screens working first. (booting is a serial process and BIOS is first) {power good, BIOS runs , POST not failing, then boots Windows or any OS}
There are Laptops and Desktops. (and worse notpads, with these hidden bad batteries)
The Desktop screen dead and you hear the fans blowing (both) in the PC case, then test the Desktop monitor first on known good PC or as it shows here.
The Laptop dead, we first remove the huge main battery first and run on AC power pack only. (if this works bingo battery is bad or worse shorted , take it away from things that catch fire, these batteries (old generation) can catch fire.
Some PCs fail and go dead caused by electrical shorts, and we do fault isolation tests to find those bad actors.
One other way to do this is to buy a 2nd used PC and swap parts until the PC works again, (some good used PC same as your can cost only $20 to $100) (even less than 1 hours shop labor costs)
Some folks like to FLASH there BIOS , just for fun or paranoia?, then brick their PCs.

Examples are below, see and read the first link above first.

 The first thing to know and avoid:
  • The laptop main battery is the first to fail, due to short life span 10 times less than the pure electronics parts inside. (as low as 1 year old)
  • The Coin cell is 7 year spec. life. replace it or the screen can do black , BIOS screens dead, black.
  • The HDD is the next short lived device,  5 years, on laptops or less dropped.
  • What not to do is  "FLASH" your BIOS Firmware,  NO do not do that or risk bricking your PC as thousands have done.    how to  Brick your PC  with 1 hand tied behind your back!
  • If the PC is silent that is  Hardware failure (except fanless tiny notebook/tablets, I do not cover tiny notebooks, most folks can not even get them open at all)
  • A HDD inside any PC (not SSD , not M.2) spins. and makes this sound when turned on. Hear that  sound of its spinning disk.
  • All PCs that overheat self shut down  at 90C, to save its bacon. The cure is simple clean it, fully.
  • All PCs have BIOS POST errors that will beep codes, blink LED codes and or show POST errors to the screen. Never ignore these warning, read you service manual to learn what they mean (DIY),
  • Windows dead or infected? , Most modern PCs have  chapter in your users guide called "RECOVERY" each maker of PC covers this differently, with  built-in recover or with sold media recovery , yes read you manual.
  • Windows BSODs (blue screens of death ) W10 as 100 different blue screens of death now.
  • Windows installer will fail to load on dead or weak HDD and may also fail, if the HDD is not blank first, (erased using these tools) ( Depends on who's install media you have, be it or OEM makers disks)
  • Avoid PCs made with the years 1999 to 2007 due to the CHINA CAP PLAGUE.

These sections below, are examples of actual failures, tests  and the cures.
If buying a USED PC, avoid years 1999 to 2009 (so there are no CCFL lamps nor bad solder ball GPU chips) or older. (or bad Capacitors from H3LL)

Mini-Menu: "black screens"
Laptops Only!
All Screens/ Monitor problems
See the  flash light test ! year 2009 and older.
Just BIOS screens dead
Hard Power Resets
can be a simple fast cure!
Desktop's Only! GPU Solderballs failed?
circa 2008 !
LapTop  power failure causes.
Rules of the road.
Basic causes for all  Dead PCs.
The logic list of tests. Desktop PSU fails
Fault Isolation steps.
To find shorted modules



Desktop black screens of death: (DT only  !)                          JUMP TO LAPTOP NOW, if not a DT?:  
See basic dead PC page first.
The RTC coin cell loves to fail after 7 years,old, and will make BIOS go nuts and some even make the PC act dead.
The minimum goal here is to get the PC's BIOS to show messages as you turn on the PC.
If you just put in  power hogging new GPU card this too can cause PSU overload and dead screens.
The monitor 2009 and older had crummy CCFL back lamps, test it this way.
There are only a few cases of true black screen is  bad monitor,  as seen and tested here.
The given is you already have  tested the monitor on a known good PC and it works ok. (with the same cables) so is PC only issue, if the monitor works on other PC's.

All PCs made send out errors many ways, all from BIOS P.O.S.T error codes by Beeps / text or flashing LED codes, do not skip these big clues. (read you manual at oem?.com , are best PC on earth)
The PC makes noises turned on, both fans spin and actually blow air. (if not you have bad power lost power in the PSU or inside the PCs VRM's have shut down.
The 2 fans all must blow air in all DT PC, and are not packed up in lint. (clean it now) If the PC has GPU video card , and it too has a fan it must not be packed full of lint and jammed.
If the PC fans blow good , we next   try another monitor on this PC or move the monitor to know good PC to test the monitor.
The dead monitor or any screeen dead page is here.'

In all cases , if  you see this error below in RED:
The monitor if turned on LAST shows, "NO SIGNAL or NO SYNC  or Video cable missing" errors.  (means dead PC)
"OUT OFF RANGE" error means the PC is using way too  high of  resolution for me the relic monitor to use, so set it to 800x600 fixes this error.
Lets say the monitor tests prove to you that monitor is not dead, (tested on 2nd good PC is fast and effective way to learn this simple fact)
Next is PC sounds.(or blink codes)
If the PC is silent or fans dead or packed full of lint, then we clean the fans first and get them going first the CPU  and  PSU fan must blow air.
The PSU must turn on,  this makes fans work and the CD/DVD tray will eject, and the Screen most POST .  BIOS screens  must  all work, and is GOAL 1 now.
A PSU with a dead fan is a dead PSU (rare exceptions, some high end PSU the fan is 0 RPM below 100watts used ,surely you know when your PSU blows air?, but in all cases the manual on our PC should answer this.
Once the PSU stays on,  and the power LED glows correctly (blinking can mean stuck in standby, reset it this way) the mother board on many PC have center of motherboard, STANDBy LED if out , the PSU is bad. (or mobo shorted or things to it)
At this point it is best to have a new RTC coin cell battery or measure it with any voltmeter made at 2.9v to 3.3v, lower is battery bad or REAL SOON.
Next is POST errors. The PC can show POST errors as beep codes, LED blink codes or POST text error to the sceen , some PCs do all 3 (nice PCs)
If Monitor tests good above, and BIOS is dead, and no Blink codes present , and fans run ok and the RTC battery is good , in most cases this is a bad PSU.
If the PSU  is good and bench tested or new, what else can be wrong, causing black screens on a good monitor.
The answer is simple you have shorted (modules, chips , devices , cards (PCI) or HDD or DVD drive inside the PC. ( learn now that anything there  can in fact short for sure ESD zapped or lightening hits)
You unplug the mouse and keyboard just in case they are bad, to see if screen wakes up. (remember BIOS screens are first not windows)
The answer for any good PSU not working or turns on for only 1 second, (ATX rules) is overload, a.k.a shorted modules inside the PC, (I use the word module to coer all parts inside, as you see them case lid off)
This was covered in my first link above but here is the direct link to Fault isolation tests, finding SHORTS.(aka, strip down testing)
If the PSU turns on and stays on , all fans glow and BIOS runs perfectly, but will not boot ,what then?
  • The HDD must show up in BIOS if not HDD is dead, or run the HDD test in BIOS if fails the HDD is dead. (I use full  Linux, demo boot media to run SMART tests in every case of windows corruption)
  • The HDD must be listed 1 in the boot order, (1st boots faster so 1st it best and not missing!)
  • Test the HDD next, no OS on earth will  ever run on a bad HDD nor if weak, or fails S.M.A.R.T tests , OK?
  • Reload windows is next.
  • If this PC was slammed the HP F11 (I have HP and this is a HP only key) will be dead, or fails recovery, the  only cure for that (out of warranty) is buy a new windows again w10 is best)
VIDEO PORTS: 1 port , 2 ports or 8: (what you see is what you got !)
(I have a GTX 1050 card here, a super nice card, and to test it we must connect my DVI monitor to my DVI , video card jack. (if you have DP or HDMI use that)
The extreme example, below, to test the video here, you can use the bottom GTX jack DVI #2, because with this card inserted the BIOS shuts down all top jacks autmatically, (on relic PC it must be set manually in the BIOS)
On some old PC there is no Video PCI CARD here and just the old onbaord VGA jack so use that,  but if there is a card there, you must use that or remove said card.
Gamer PC, up to 8 video ports  (most owners of old PC's have 1 or 2)  A best choice for a PC if ever there was is this.(future proof )

end desktops. (I do not cover ALL_IN_ONE PCs at all) 

LAPTOP black screens of death: (LT)
The laptop moves the screen inside, making it much harder to test.  (and easy to break , in mobile abuse/use)
This section below LT only  is in adjunct to , basics tests here.
A laptop is mostly just Desktop shink.
  • A large battery added, to run off the grid (AC) and a on motherboard charger chip
  • They moved the PSU (front end only) outside the PC in a AC power pack mine does 120VAC input and 19vdc out at 90watts. (more watts is ok)
  • The then made the case non standard (non ATC spec) and hard to work on as can be possible even to the point , no screws (sux) and snap apart casings, that love to break.
  • The laptop has a built in screen and keyboard and virtual mouse.
  • Add to this a more frail HDD.
The tests are the same using the same diagnostic logic in your  head.
In this order only:
  • Big battery out first; they are short lived, and love to short and overload the PC, so get it the H3LL out first, in fact some even leave it out FOREVER ! (with no need for off grid or mobility )
  • Do the long power reset next
  • Make sure the fan blows, (seen , heard, and felt) if not power is bad, that means power pack or VRMs are dead or only overloaded on the mobo (motherboard)
  • Next just like DT, the screen must glow, with words, logos's , post errors or something if not we do the CCFL dead?, magic flash light test next. ~2009 and older PC.
  • IF the CCFL is dead, use any DT, VGA monitor connected to the VGA port on Laptop rear, to see if PC is running OK.
  • Just like the DT, BIOS screens are GOAL 1 now. This point in the diagnosis FIRST.
  • Of the CCFL lamps are good, and the PC seems to turn on, fans blow, then next is what, the RTC coin cell just like DT it goes dead at 7 year max.(spec) 2.9vdc,not below.
  • if the PC will not stay one it is either overheated or PSU overloaded
  • Ok it turns on now.(and stays on)
  • I then check BIOS to see if the HDD is present, if not it is dead, if it show there, try to make it 1st boot device in boot order pages of BIOS.
  • If you can find it in BIOS under service, or maintenance pages, run the HDD tests and memory tests,  if the HDD is failing this is a bad HDD and is FOR SURE BAD. replace it.
  • We then run linux tests on the HDD called SMART test.
  • Ok smart tests pass,what next.? easy.
  • RTM your laptop (by exact model)  has users guide read the manual, and see that chapter there on RECOVERY,  this chapter shows how to reset windows back to day 1 new, (all your data gone as will  be your APP's)
  • or buy new windows and load it.
  Warning just like I  stated in my DT section, if the PC was slammed, the RECOVERY  by your  OEM maker is now gone or now a wreck. ( HDD replaced before, or using non OEM disks to restore is slamming it)
Also some virues can wreck your Recovery partition on the HDD.
Most PC over 3  years old the Maker does not sell you new OS media install kits, (that you lost or forgot to buy 10  year ago?) I say 10 due  to at that age most OS there are DEAD.

The AC power pack creates DC power and goes to the LT D.C power jack its 19 volts Direct current that any meter can measure if you want. Below 18vdc is  not good.(hp rules , yours are diffrent)
A common fault on cheaper LT is the DC power jack .
Some LT (poor grade) have the 19vdc coax jack soldered direct to the MOBO, and all fail every one does fitted out like that.. This is bad news.  (fixing it can be very hard work and  special tools)

Simple ways of progressive stripping down any PC made, for sure to do any fault Isolation.

Bad things in electronics can be:   Keep an open mind , there are lots of failure modes.
  • Dead
  • Weak. (HDD can be weak, Smart tests fail the screen can be dim)
  • overheating
  • Loose parts or cables. ( re-seat parts, or wiggle them to see if they wake up?)
  • Intermittent PC or some device.
  • Soaked in coffee or Cola.  (contaminated) or worse, there is always worse (dropped in lake? or far worse the Salt of the Ocean?)
  • Some can fail and make noise, electrical noise that closes other things (and it) to go nuts. (bad PSU or bad caps top this list)
  • OR SHORTED OUT, any chip, module, or capacitor or transistor or most things seen inside any PC can in fact short out  and when that happens it shuts down or will not turn on. Click Fault Isolation above.
  • Frayed power cords, or Video cables ends. (bent pins on VGA plugs)
  • Noises, not normal are pending doom. (or the reason the PC is dead now) fans making bad noises (bad , filthy or bad bearings) or HDD clicking or screaming load .

Just BIOS screens dead?,  The fans working.( running on AC only power pack no big battery)
The Laptop is the VGA screen port dead too? if not dead there, the LCD CCFL are dead in your Latop.
If both are LCD and VGA external screens are dead  the  GPU chip (2008) is bad
The RTC battery dead on some PCs can make the BIOS go dead or just show CRC errors to the screen.
The only sure way to find this is here.

MORE EXAMPLES :  All the below are real life case examples of extreme diagnosis of  a top grade 10 year old PC)
Laptop Case top off. " DC POWER" checks:   A LAPTOP HP Elitebook. (has many parts to fail so is a super good example)

I get to my power connector inside, LT and and with my magic voltmeter it's 19vdc on those 2 pins there,  turned on, telling me power is okay.    We can use a $20 DMM meter from Walmart ,to do this test.
If the 19vdc power  is low, say I measured 15vdc ,I'd try a 2nd pack if its low, then the laptop has shorts. ( I have a 4 ohm 100watt test resistor I use to test my power packs, by them selves. )
Not clearly and carefull that nasty old BIG battery is first to go (removed), and is gone below, not byaccident, but on purpose.
I checked the RTC coin cell first thing, 3v good. next.
One PC had shorted land line modem card, I pulled it and the BIOS screen POPed.  what useless that card is and is shorted.
I can remove many things off that MOBO.
First tests are with 1 stick of RAM not 4 and to test all sticks 1 by 1, (I have 2 slots, top and 2 slots bottom ) the service manual covers this.
To see if some option there is shorting out power.REGS (VRM) like: (video card,wifi,bluetooth card, DVD drive, RAM, HDD, secure card reader card, SD mem. card, and more , keep and open mind, anything can short out)
To see if Blink codes  change or  go away as I pull or add things,
Warning never hot plug parts, ever inside any PC. The AC pack is pulled and the nasty big battery was out at all times here, and I push the Power button and this discharges all CAPS in the PC, and now is safe to work.
Wait 5 minutes now, just in case.
Now with a ESD wrist strap ground clipped  to that copper heat pipe seen here I begin to work.
See , me doing magic testing here?
Note the case is missing now,  this allows for the most fast testing of any dead PC for sure OVERLOAD.
I have almost all things pulled here, but not CPU/GPU, even the fan can be pulled for 1min test to see if BIOS wakes up, keep a wide open mind on what can short (answer is ALL THINGS CAN)
See my A.C.  power line left top? MOBO, See LCD? that just plugs in? See a DELL USB keyboard there, (original key board is not plugged in)
If the screen is dead (LED here) we then can plug in VGA DT monitor at the rear VGA jack and see if that works and gets BIOS screen seen below.
 See fan spin fast? at power on? it must,  See BIOS work?  I could even boot to windows if I added the HDD now.  (no loose Heat sinks allowed)
Do not forget the BIOS has a Hard disk and Memory bank test. Run that now.
I do most my tests on an anti static ground work pad, and cardboard of that.
 The only rule is to never run the CPU  with out a heat sink. (and a working fan)  That cooper pipe below must be fitted correctly at all time.
The unseen heatpipe Radiator is on the left side of fan, and loves to packup in lint and make everything here overheat.

  2011 made PC HP8540w
Below is my 8540,  one can see there are 5 modules you can pull to see if BIOS wakes up.
  • I have 2 power packs so I try both.
  • All USB devices removed.
  • Screen pulled and VGA monitor screen used external,or run the internal screen only and pull that VGA outrigger card,  thinking it can short too.
  • Pull all RAM but 1, then  try each 1 by 1. In bank 0 slot, only.
  • Pull the  stinking  useless dial up modem card and leave it out forever.
  • Express card. out.(but doing so kills dead it's status LED,  but is not problem, to get BIOS working.) a secret I tell you.
  • Wifi card pulled.
  • I can even pull the GPU card, that kills all video but  to see the PC blink codes for lost GPU; report ? Caps lock blink codes.?
  • Watch out the USB3 ports are dead in BIOS.  only USB2 work at this LEVEL ! (secret #2)
  • The CPU never fails, but loves to overheat with bad fan, or it's radiator packed in lint or the TIM is bad, (thermal grease)The Intel chip here shuts down at near 90C, so learn not to  let that happen !
The CPU will wake back up when cool (let it)
You can pull any module you want to see if problem ends, and  you will get Blink codes for most pulls.
We do pulls to find shorts. (1 small example say I pull Mister WIFI  module and the GPU wakes up. that means the WIFI was shorting the power or data bus.
Learn that there are two brain chips here,  the CPU, and the main power control processor that can blink LEDs even when the CPU is removed !!!! If this test fails the MOBO IS DEAD. (a dead power control processor)
5 modules pulled, PLUS  HDD and DVD, (a spare GPU card is a nice thing to have , spares are like $20 used and lots sold used on feabay)
5 modules to pull.
Keep in mind GOAL #1 get BIOS screens working and then GOAL 2, get something anything to boot.
On mine I can pull, modem, wifi , VGA outrigger card, the whole Express card assembly comes out. This card Express has the power status LEDs so if pulled you lose this information.
This PC loves to Blink the caps lock keys, or Numlock key LED's in fancy codes. but not if the CPU is missing.
I can even pull,  GPU video card seen here, Keeping 1 RAM stick (DMM3) and one CPU,  this mobo even has a Blink code for CPU missing, (yes)
We pull things why? Answer to find things that are bad shorting out critical power buses.  Shorts happen. we find them this way. (learn that ALL THINGS can short out)
What do shorts cause , answer, it overloads the power bus system and kills key functions in the computer.  (or worse)
See the DVD drive pulled, HDD pulled.

No two Laptops are the same, parts locations, (there is no standards here) Only you can read the HP service manual and see what is there, and not.
Taking any LT apart like this takes, some  skills. Lucky me , HP has screens an not those nasty, blind snap in parts. (HP and DELL RULE)
It is not a casual practices like it is on any simple standard DESKTOP.
Some LT are very difficult to take down (not this PC) and must be done in the correct order, and not breaking fragile parts.
Amazing enough the HP service manual covers all these steps.
Most Laptops, have no GPU card like above, on mine the GPU was upgraded by me.(easy) Seen above as GPU. card.  (I buy laptops that have a card here, or don't buy that model)
Keep in mind that some USB3 ports will be dead, until the correct HP drivers for it are installed. (that means use the left  USB2 ports to boot from any LIVE CD BOOT sticks (Linux or Windows PE)\
That also means testing USB keyboard at boot time, use the USB2 ports ONLY,  not my 2 USB3 ports seen on the top right. My BIOS does not use them.
This PC can boot to like 7 things, HDD1/2 ,DVD, SD card, USB2 ports.
If the BIOS works now, and the HDD/SDD will not boot, and  the boot from Live Linux
If linux runs good then the harware is OK.
If the PC was not slammed, then F11 works (RECOVERY)
The HP hot key for RELOAD the OS is , F11 on mine, power on , tap, F11 (older HP PCs usee F10)
Go to and get the OS recovery Media kits to reload the HP software, on any HDD that was dead or replaced.  ( only sold 3 year or new says HP)
Do not turn on BIOS or HDD passwords or you will real upset later, when you forget it. (unless you work at CIA/NSA/DOD avoid that)
If you see this, it's not a dead screen at all.
This is the GOAL getting to  here,  this is my MAIN BIOS screen on my HP 8540w . 
Best unless a super geek that keeps records, stay the H3LL out of the Security page. One can even turn on BIOS finger print mode. 

Here is the first BIOS page, that lets you go to all BIOS pages, inside the FIRMWARE EEPROM.
I pressed F10 to get the above screen. These screens all prove the PC Is not dead, nor is it black screen of death PC, But is the first goal.

I'm not going back to 1979 this old HPs 1984 first laptop, ever.

Rules of the road, BLACK SCREENS 100% and if you want to be electronics, savvy: 
  • Is  "first do no harm", (why make it worse?) (flashing bios for fun or hot wiring parts you do not understand)
  • Try a hard reset.?
  •  Power is first , not just the power cord to the wall; is LIVE AC okay,  but all DC supplies, and regulators must be good , no power ?or  there will be no joy.
  •  If boards, cards, batteries, modules, or anything is shorted, you will not get far, until that is corrected. (unplug as many things as you can, even USB things. and if brave , things deep inside, or get a technicain to test it)
  • If the fans are dead, that is  big clue. (CD/DVD Eject button dead,  means power lost)
  • If the old HDD makes no sounds at all (it has and electrical motor inside!) then it is DEAD, or unplugged, or the PC has no power, (sure weak power, 6vdc for 12vdc the motor will be dead) If the drive clicks madly it is BAD.
  • IF  the DT monitor  is 100% dead, and never once even shows some white text,  that meand the DISPLAY is dead, turn the monitor on last,  if it shows , NO signal , NO SYNC, the PC is dead.
  • If the LT screen is 100% dead most times that is the LT power failure or the below. (bad battery , bad power pack or both) Laptops (LT) can run with no main battery endlessly on AC power pack good.
  • If BIOS works ok, or acts odd and the  time and date act odd or BIOS forgets things, the COIN CELL IS DEAD (3v Cell)
  • In most cases the PC is just collection of 5 to 10 modules. One is bad, now. (you can GUE$$ or test, most times Guessing will be very very expensive. (one guy bought 3 mobo and keep inserting a shorted wifi  card each time)
  • Do not work (dismantling) on the PC (or monitor) with it plugged in the 120VAC wall power, hot line Power,  or the HUGE BATTERY inserted, some LT have 2 of these, some in place of DVD bay.!
  • Do use ESD antistatic measure, (google that) a ground strap on the wrist is best , easy and cheap.
  • If you keep your hands out of the PSU guts you will not be shocked with 12vdc ever.  
The first rule in all of  electronics WORK, is never hot switch(plug) parts, INSIDE, means plug or unplug THINGS,with power still turned on, and not discharged first.  (learning this the hard way will cost you big cash) \
Do not hot swap any PSU power jacks inside PC's.
Exception 1: USB ports are fully hot switchable as is the eSATA PORT.(BY DESIGN)
Almost all electronics have huge capacitors inside, that hold a powerful damaging potential charge  and ignoring this one fact, many folks (noobs) blow up good parts in the PC.
If you like to swap PCI cards like crazy ignoring those hot power pins  you will blow up that Card ,the MOBO or both. Just unplug the PC and push POWER Button for 10 seconds or more. The play card swapper.A
The DT has but one power source (2 counting the coin cell that is safe to leave be) unplug the power cord and push power button.
LT(laptops) can have 3 or 4  power sources. (AC pack, 2 main batteries, (1 for sure 2nd is advanced options) and the coin cell again.  The coin cell in all cases is a harmless device.
Remove all laptop main batteries, then remove all power cords  then push the Power button for 10 seconds, now the PC is safe to work on. ( no need to blow up good parts now)
I have workstations with hot swap SAS drives, but I will not cover that now but did here. I am doing PCs only above, not work stations nor servers here.


  (all) A short History and lots of tests and cures.  See all monitor issues , here.
This screen shows the PC is not dead, nor is the screen but my not boot windows.

This is not a black screen of death, at all ,see the HP logo? , these words from BIOS?.
The above shows me the you have power, CPU works as does display, and memory and the BIOS is alive, and the HP logo is from the BIOS code.  I'd say if you can't get a boot from the HDD NOW, then HDD bad or the OS is corrputed,  Go in to BIOS now and click HDD tests.
If you F9 booted to say a Linux Live disk or usb memory stick boot of Linux now, you learn that the whole PC is ok, but only HDD is dead or its OS IS CORRUPTED.  My F9 key at power on allows me to boot to vast things. 
When I say HDD, I always mean both, HDD or SSD , which ever is your case.
If you can get this screen and  a boot CD works (Linux live or Windows LIVE PE works ) or same way using the USB memory stick boot, then the PC is basically ok.  (that means the real problem is, HDD failure or OS corruption)
If the HDD tests pass, (learn how to test HDD and save data) then the OS is bad. end story, hit F11 and reload OS.  (if F11 key  is dead, magic restore , then you need the HP media kit to fix that.)
On older PCs F11 is F10 restore HOT KEY(if the HDD was ever changed out F11/10 will be dead ) leaving only one solution. the media kit, from HP.
On even older PC's, there is no such restore HOT key, (some are named Compaq) and you need the media kit to recover Windows. (click kit link above)

This page covers all screen and monitor class failures and tests.  for all montor issues go here.
Logic way to diagnose black screens. (I will do jumps here to solve the problem) My attempt to make the shortest list here. (above arefull detailed checks)
(Ill assume you are not standing in the sun, or the screen is dim or the screen has words (words there means it's not black )   Dim screens are caused by ,  these things.
If the PC beeps or Blinks, Cap locks keys, stop now and learn what those mean, first. (it is telling what is wrong, and only HP books cover this....period)
  1. If a laptop , does the flashlight trick work? seen here (if this test passes the LCD black lamp is dead, the PC  is not dead)
  2. No, it is a Desktop so does the OSD screens work seen here.? if not the monitor is toasted. (end story) If a spare monitor works then the PC is  ok, and monitor is not. THE OSD must work,.
  3. If a laptop ? does taking out the main huge battery cure the black screen issue? yes, replace it, if not, continue on.
  4. Are all  BIOS screens dead, too?   No, then this is not a black screen PC is it, its a NO BOOT PC, and that is solved here.
  5. Ok BIOS is 100% dead, no HP/COMPAQ Logo or text telling you to hit ESC to enter setup (hp BIOS).  The flashlight trick also fails to show data of any kind in step 1 or step 2 fails above.
  6. All screens fail, even test screens on DT or LP rear VGA port.  Then we work a dead PC base. (desktop case or that which hides under the Laptop)
  7. The Laptop we check for 19vdc into the mobo now using any voltmeter,  the A/C POWER PACK must be good . if not?, try a new power pack now.
  8. In all PCs are the fans dead? or packed full of lint and jammed.
  9. The Destop PSU is dead if the fans are all dead,  PSU fan , CPU fan and if  fitted, GPU fan.  DEAD PSU's happen.
  10. Ok the PSU seems to work.  the DVD enject button works, the
  11. On desktops we have 2 VGA jacks (or DVI or mix) one is Mobo jack and other (optional) is the PCI Video card, are both dead, even pulling the PCI card now and testing the mobo VGA is wise , now,  or putting in a spare VGA card in the PCI slot to test this path.
  12. Windows 95 PCI card that works.(or this $5 card from years ago)
  13. Ok still dead screens.  Pull all RAM and try each stick 1 at a time.
  14. I now pull everything off the MOBO , (except CPU, 1 ram,  one VGA port  but I can pull the DVD cables and hdd cables for sure. On laptop top, pull all devices like that and more, NIC cards, etc.
The Key tests: listed again.  KEY EVIDENCE !
  • Beep or blink codes.  count the learn the code, write it down and read the HP service guide on you PC for the causes. (keep in mind weak power can make the codes lie ! or any shorted modules inside, that cause weak power)
  • The screen really is black even when BIOS hot keys are used !
  • The flashlight trick works or not, on all CCFL screens made,  2010 or older mostly.
  • Fans dead or packed in lint.  all fans, desktops have more fans all must be watched, and inspected.!
  • HDD is silient. 100% no noise from it will not cause black screens ever, but will cause DEAD OS, (dead windows for sure) (please do not try this on any SSD but Hibrids yes.
  • DVD (or CD) tray  button eject is dead.
  • On modern Desktops with high end mobo's my ASUS has a green PSU standby lamp if dead, means the PSU is dead, or line power A.C. is dead.
  • The Laptop runs with no battery. 
  • The Laptop runs with the correct 19vdc power pack. (not using power pack off other PC's)  65watts or more.
  • The PC runs (any) with module removed.  Yah ! parts can short. for sure.
  • Smoke coming out of PC, sure can happen, seen it vast times. For sure in PSU's (cheap)
  • If PC has 2 VGA jacks try both,  ? then try 1 VGA port with the PCI VGA card removed?
  • If fitted with VGA PCI card did the AUX power jacks fall off. seen here.
To test any PC and all the above fails. we strip it down to near nothing to find shorted modules of ANY KIND. Laptops.
Desktop  too, even to the point of bench testing them , called a minimum system.
Minimum system means just that,
MOBO + PSU, + power botton + CPU(with working fan)+ 1 stick of good ram (DDRn) in bank-0 !
Then 1 VGA card PCI-e  or the on board VGA /DVI , if fitted., some mobo have no on board VGA chips and must have PCI-e card added.
If you don't have a spare VGA card , PCI, buy one for like $5 used and keep it in your  spares box. (for testing)  Would you not be happy some day and the $5 saved a $300 labor bill?   yah..
Connect up  24pin power connector  and a power on botton,  until you know the pinout of the power on jack pins.  If you know that you need no power button to test this MOBO, ever as see below...
With any VGA monitor connected the Screen must show BIOS screens (on demand)
A Bad CPU are rare, pins not bent. (fan works, and heatsink compound not like hard as nail dried glue and cracked this old glue  like compounds, top grade compounds do not do that.)
See the VGA onboard here m5a78.  If VGA port is dead, add a VGA card in the PCI slot to see if you get SCREENS now.  Below right is ASUS M5a99fx that runs the 8 core, 5GHz, processor by AMD. (ASUS is a top maker and recommended by me)

There are 2 tricks to change from VGA onboard to VGA in slow, on new PC its automatic, if PCI-VGA is installed it goes there first. , on older MOBO you must change this inside BIOS. (on/off, onboard,  auto or order, (PCI first/PCI last)
MIN, System. photos next.
Found on the net this , nice photo  One stick of good RAM is necessary,  A case is optional . The VGA card is optional if you have  mobo like the above shows.
The below a TECH is testing his MOBO before the swap, (a savvy guy  he is) The PSU can be bench tested or in the case, seen here.
Do not use ESD conductive foam below the Mobo, doing live tests.  best is a dry brown cardboard box piece.Never use plastic, it is a ESD killer material. (if the GPU card has AUX power connector it must be used !)
  No mouse or keyboard needed to see BIOS Screens, "hit ESC to enter Setup" (HP BIOS) but if seen the keyboard is connected and ESC hit.
The ASUS hot key is  DEL key. btw.
This next drawing shows, (only on ASUS) the power pins to jump if you don't have  a power switch or is defective, , with a screwdriver tip jump PWR to Ground next to it, do not hit the +5vdc pin ever.
All top brand MOBO makers have this custom diagram, in the manual for this exact mobo. There are no standards here on THIS powersw JACK, maker to maker.
Try not to short the +5vdc pin.
this is how to cheat and not have power button, just jump pin PWR to Ground pins see at redline below. BAM it powers on.
The power switch is a normally open , momentary closure switch ,  do not  leave a jumper there shorting PWR to ground, endlessly.

The word RESET. (said by many and not clear at all , why?)
First off the PC has many types of resets.
(endless counting all resets inside of windows , reset IE , recovery of the whole OS, many applications have a  reset or  in W10 settings window see resets, or reset PC to saved recovery point, or setting type RECOVERY)
The PC has PassWord resets.
BIOS resets. (in the main BIOS page, click set BIOS back to factory defaults )
Locked up in sleep mode Resets.
The OEM PC maker also has  RECOVERY, overed in your missing  users guide?, read that at your makers OEM pages ( etc) Or buy windows and install it fresh.
My HP PC the recovery mode has hot key, as many makers do, and on mine is the F11 key, I power on and hammer the F11 key and the recovery magic partition wakes up and you can reset HP back to day1 , if the HDD is still good. (or not slammed)

The forced power reset :
On laptop pull the huge big battery first. if it is there and comes out easy, remove that first.
Unplug that power cord from the wall AC power jack.  (ending AC power)
No push the power button and hold it for 10 to 30 seconds, and release.

One can also pull all batteries with the RTC battery  too, removed , if at wits end. 100% zero power total can win the battle, (if chips are latched up from ESD events, for example) (up to 3 batteries possible on some LT)

Version 11  5-9-2017  ( a work in progress)  I'm retired but not dead. 44 years of experience, to year 1965 , edited 11-13-2018 , moved basics off page. to dead-PC. added GPU tests and PSU exceptions. May2019.
 By : DeadPool.