Desktop GPU Video card update/upgrade H3LL !           
                    If your PC is near  new (2014+) (or 2020 and is UEFI only PC, learn that old cards do not work now in full bore max UEFI class3 mode) see why it can suck here.
                    Lets talk water cooling: (some GPUs' at or over 200watts love to over heat)
                    or the problem really is just wrong usage of video adapters (port connected inline)  This is common if the new card does not do what your old monitor needs (DP card and monitor is DVI only?)
I made shorter list here:

You bought a dead PC or with dead GPU card, and the monitor is dead black , and BIOS seems dead? (BIOS hot  keys are dead?)
Or PC ran great before you added a new GPU card?
Most gamers are going to buy a card that supports DirectX 12 GTX640 up (newer)  or
Radeon R7 240 up.  A GTX1050ti is  great choice no new PSU needed, bang for the buck or R9-380(x) (200w).
DX12 is backward compatible and the game decides not you, and forget DX9 for XP it's dead.)
A good PC choice used and at a great price is this DELL T3610. (2014mfg) < see my GPU tests here.
  • PCs can have no GPU card and only the iGPU (onboard mostly in the CORE processor) or the PC can have GPU PCI-express card, The BIOS needs to be set to one or the other. (first)
  • A high end GPU card, may need a bigger 500watt PSU, or more.  R8-380 does.
  • If failing now,  then do the long hard reset.
  • Make sure the RTC coin cell is not dead, if dead the BIOS or even the power button will be dead. (did the power button wires fall off the motherboard>?)
  • If still dead now that is DEAD PC for sure if all fans are silent.
  • If the PC was just found in fleamarket or garage sale, make sure all jumpers on the mobo are set correctly (2 to 4 found), (RTM read the manual on your PC no 2 PC are the same)
  • If PC is really dead see this.
  • If using a video jack  adapter device, or conversion cable to make video work , they can fail.  Use only direct connect cables to VGA/DVI/HDML or DP) in that order.
  • New card, iGPU works but not the new card.?
  • The new card must fit and not hit , THINGS (hit RAM, hit fan casings, hit front panel connectors, hit SATA cable jacks, hit the HDD cage) Measure you case and buying carefully is best. (measure once ,cut twice?)
  • The new GPU card may need 2 more AUX power cables from the PSU to  run , if see there, is surely must have this connected and PSU that has the correct rated wattage for the whole PC and new GPU card.
  • If first time using  any PCIe video card, in the X16 slot , first remove the video driver, in device manager, then reboot  the PC next.
  • Set the BIOS Video page to  1:Auto, 2:PCI-e GPU 3: CORE HD iGPU. (pick #2 or auto#1 Some cheap PCs are mode 1: auto  and can not be changed so they auto change with GPU card Insertion.
  • In the main BIOS again, turn on , enable OPROM extensions. (turn off secureboot and use CSM mode to set up the card) The first goal is getting BIOS to like the card, and screens work in BIOS.
  • If the PC has windows 10-64bit  installed , and was setup to secureboot,  and you need to make changes to BIOS, you must turn this off first. Then boot to BIOS and make changes then turn Secureboot back on.
  • Exit BIOS and save on exit (picked)
  • If you have trouble getting into BIOS , unplug the boot HDD0/SSD0 boot device.
  • Then install the new GPU card ,  what fails on new PC locked in UEFI CLass 3 mode, old GPUs can not be used no ( kinda moden day H3LL that, after all we can use any GPU card on older PC's)
  • Be real sure the Video cable is moved to the new card, jack and do not use 2 video cables now, just 1 for now. (if the card has 3 video ports , use  them in this order VGA/DVI/HDMI/DP )
  • Now some more pitfalls in new GPU cards. (see heat problems)  (learn that modern GPU's will slow down too hot, or even stall)
  • Not having a PSU, with enough wattages, 500watts or more is best , for sure now or going to any faster card later , even next year, some gamers up grade every year.
  • Not connecting the 1 or 2 AUX jacks seen below (if only1 you need one if 2 you need 2 cables)
  • Not having a newer V2.3 PSU and the 2 cables below are missing.
  • Do not hot swap any  parts inside any PC. (this needlessly stresses chip in your PC why in the world do that on purpose? , in my book dump it is)
  • If PC fails to show screen data of any kind , BIOS Dead, no text, no text errors, or no OEM logo's , then do a strip down test.
  • Some junk class and  cheap  PCs, the main X16 slot for GPU is limted to 24watts (SFF dinky do , PCs)  avoiding them is the ONLY CURE. (hint buy full sized Desktop PC's of you want to upgrade later)
Just photos of common parts below, and unique problems found with GPU upgrades.

This 2 jacks here (if seen) are never optional, some need at least 13 amps each from the PSU 2 rails that feed this card.
Some need 365watts just for the card, 100 to 200 watts is more common today. 
The RX Vega has two, 8 pin aux, jacks (6 yellow wires at  6 x 9amps is 54amps and 648watts but 345w possible ) The PSU must be up to that task, of not the card dead, card artifacting or crashing.
That set of AUX jacks yell,  over 75watts needed for sure.

The correct PSU plugs are here. Note modern 3 yellow wires not 2.  The above card need these 2 cables (ATX PSU spec . v.2.3 or higher)
A RTX2080 needs 2 cables, 6 and 8, do not leave either unplugged. (use adapters if you must or a better PSU)

THE  video card can use any of the 2 left below photos cable, but never that EPS  8pin, ok.
That  Atx12v is mostly for CPU VRM's plugged in to all modern motherboards MOBO.
The green/blue sense pins are NOT POWER they are feed back for kelvin load sensing and correction. As you can see, the 8pin is the most powerful, see why, 3 yellow wires, and good to 27 amps.
What matters is the # of yellow cable wires from GPU to PSU,  more is best. (the GPU designre knows how many to use, do not use less)
Top High end GPU cards use connectors , that can say handle 200watts, some need 300w. or RX Vega at 345watts just the card for $500. with two 8 pin jacks seen here.(use a 700w PSU)
The RTX2080 (some) have one 8 pin and one 6pin jack and the card comes with 2 adaptors to pull this off. (many PSU have on PCIe 8pin plug)

The magic split , the nobody understands and not one card maker publishes this. (sadly)
First off no 2 cards are the same ( not same SKU#). The currents on say the 3 rails add up 1 one number,  (say 200w) but the split is NOT TOLD)
Why does that matter, easy, picking a PSU.  (so one could just guess.,  (200watts is 17 amps lacking split data make sure all 12vdc rails can do 17 amps or more) crude but effective.)
A Corsair VS Series, VS500, 500 Watt, has a 40amp 12v rail.
New PSU do not have 2 to 5 ,12vdc rails now, new fire rules nos allow a single 40amp and larger single rail, and lots of yellow wires landing on a single point in the PSU.

New PSU's have single  +12vdc rail but with up to 8 yellow wires leaving that PSU solder pad. (new rules now)
The older PSU's had  up to 4 , +12vdc rails. (real or virtual rails) and each with its own spec. for power.
Even older PSU's have huge amp ratings on +5v and 3.3v rails.  and very little on +12vdc. ( finding new PSU  that has that but addes lots of power on the +12vdc rail can be a hair puller) The cure is not use PCs that old.
This means LOOK and see what you have for yellow jack/plugs, total amp ratings each and if that is sufficient to run your new GPU card.

Best is  700watt and end  the guessing here, the AUX ports on 300watt GPU use  huge current flows, buy a PSU that has extra watts (it is not wasted the PC only uses what it needs ok?)
Facts are the GPU cards have up to 3 rails and are seperate and have 3 separate GPU VRM regulators. ( best site covering that is here,  very good.)
Most times if 3 rails?, the PCI-e A1 pin group socket rail can be limited per spec, at very small 25 to 50 watts and  not the ATX spec normal of 75watts.
A GPU card designer will try  to keep the PCI B1 12v pin group using  less current, due to not wanting to overload the MOBO 12vdc  POWER traces.(PCB  lay out limits)
That means the 2 upper rails use  more current. (add 50w to the upper rails now)  200w card is 50/75/75 or 50/50/100, you don't know splits and neither do I, but plan to be suprised or overkill the PSU.
So use the uncertanty principle and do the shot gun overkill trick. ( and the larger PSU runs cooler and longer, and can even be better quality with this size range and up)
In  this case I use a 500w PSU. (200+100cpu+50w for mobo = 350 watts need so add 150 more for margin, a sailor calls this freeboard. (add for the unknown and win)
Some PCs (mine) have 4  or more HDD, I add for that too. 25watts per pop.

A modular PSU is nice feature, not plugging in useless  3 legacy cables, and now air flows better and cooler.

Next is PSU jacks seen on all modern PSU  , but forget  floppy and no more 4 pin DVD/HDD PATA RELIC IDE power plugs.
The first 4 plugs below are PRIME now. ATX SPEC.
This is my DPS grade PSU, with removable pig tails.

The Ugly Ducklings we own: (and to avoid) Never buy tiny DESK TOP PCs,  buy full sized and RTM, read the manual to make sure it has no  limited lame PCI-e slots
Last is this very odd duck power limit  horror , not 75watt as it should be but 25/35/50watts.  (that means while gaming it might  BSOD'S at full speed )
Even the full sized Dell 790 , not just SFF PCs. small form factor.
That being said, my 790 MT PC runs a 200watt GPU card all day with FURMARK running. Devil be damned the slot limit.

This can fail only if you are gaming.
Learn to read the spec on your mobo, first.

That 35watts means GPU cards, as most all other PCE-e card on earth never ever go that high.

Power is a complex topic,  (power = watts) and the PSU is first, it must support the currents on the power rails used.

The power traces here are DINKY DO. (tiny and lame) B1 pin set of  5 pins in group +12vdc.

Power rules to live by:
The PCI-express slot X16 is limited on ATX true  PCs at 75watts max and will all run GTX1050ti.
8-pin (left) and 6-pin (right) power connectors used on PCI Express cards are not all the same.
The 6 pin can be 2 yellow wires or 3. (3x9 is  27amps max just on wires and pins.)  2x9amp is 18amps max., on old PSU.
The 8pin is 3 yellow wires, and does 27amps max.
The card needs current and if the card is 365watts it might need 65watts on the PCI slot and 300 on 2 AUX jacks 150  each, maybe.  (no card maker tells the 3 way split of power, sadly)
Learn to read you PSU AUX power cable current limits. first. and must be greater than the cards needs.

Optional connectors add a 75 W (6-pin) or 150 W (8-pin) power for up to 300 W total (275 W + 1150 W).
Some cards are using two 8-pin AUX jack connectors,  and these methods were added to the last versions of ATX spec;.but will cost you big money to buy it and read it.
This configuration would allow 375 W total (175 W + 2150 W) and was standardized by PCI-SIG with the PCI Express 4.0 standard.
The 8-pin PCI Express connector could be mistaken with the EPS12V connector,(if you do that BOOM it blows UP) which is mainly used for powering SMP and multi-core systems ,servers.

Then there are PCs and mobo that are not truly complaint to this.  (power compliance and data communications compliance are the same thing, the power limits can be wrong or ignored by the maker)
  • PCI Express x16 Graphics 150 W-ATX Specification—Published in October 2004, this standard defines a six-pin (2x3) auxiliary power connector capable of delivering an additional 75 W to a graphics card directly from the power supply, for a total of 150 W to the card.
  • PCI Express 225 W/300 W High Power Card Electromechanical Specification—Published in March 2008, this standard defines an eight-pin (2x4) auxiliary power connector capable of supplying an additional 150 W of power, for a total of either 225 watts (75+150) or 300 watts (75+150+75) of available power.
 Related is that fact that PSU spec, now deletes the 20amp rule on 12vdc rails and now rails are up to 138 amps, 1600watts.  (the pulled that rabbit out  of a hat, and tell you the wires are now VW1, fire proof and safe to catch fire)
My guess is my new DSP PSU has OCP set a tad over 46amps (12vdcRail1) sorry not testing that today. (not me)
The GPU Makers are lazy dogs, if they spec'd out the card for all 3 rails, things could be easy.
What I do is over kill this, giving all you see here, if the card is 200watts and CPU is 100w. the get 500watt PSU, a new one with huge  12vdc rails. (always add some extra watts or you can be very sorry)

Heat problems:  (go water cooled? see next frame below)
  • Heat problems?,  the best GPU card sends all hot air outside the case, using a vented GPU "J"-bracket to do that. (hint: not dumping its heat to the  inside of the case)
  • If the room the PC is in (or closet) is at 95F temp or higher you will fail.
  • If the case fans can not keep the inside of the PC cool this too will fail. (some GPU belch heat to the inside of  case others far better do that only to the rear of PC NOT inside.)
  • No better way to keep a PC cool is water cooling or a very large fan (larger are more quiet) on the front grill of PC, (hint, buy cases that allow that)  This also keeps the 25watt south bridge chip cool too.
  • PC filthy?

Water cooling , Agua.   Remember to call a plumber if these things leak, ($600/hr Union labor , LOL)
(Physics) Water conducts heat 22 times greater than air (at sea level)
The best way to go water is with an external water radiator seen below and is 100% silent and no fans. Sold for about $100 the money you spend here, saves a bundle not needing to buy a new PC case.
These great cooling tower RADs,  move the heat 100% (of captured) out of the confines of the PC case , a best of the best idea. For extreme gaming or like usage.
Imported Air Convection cooled Radiators (I'd say nothing beats this RAD)

The other way cool things, is to find room inside the PC for this RAD (copper shown)  (looks just like car Radiator below but smaller, for  leprechauns cars?.)  
Most times a new PC case is needed, and with space for this beast and pump and hoses. (read more expensive that)
The rules of Physics means that a larger Radiator, needs no fan or one that is only one large slow turning (RPM) fan (read quiet.  (experiement all you want here learn what your PC needs)
This RAD needs a fan, in most cases (no pun)

The fact is the bigger RAD can have a thermal fan switch that does not turn on  the fan on until near 80C? and that means silence until it is really needed.
A black RAD works better. But Copper is 2 time better than Aluminum (I have no spec on black anodized aluminum which is best for Alum, my guess is a toss up?)

 The hard way to do this is seen here in the vast numbers of water cooling kits.  (even cheaper if it fits your case)
(hint#1 always build your  own PC and buy water cooled case with space way up  top for the RAD and grill up top)
$500 Kit #1 ( EKWB)  (overprices in my book)
Make sure you buy and use a  fan controller (smart)

Or the imported $100 kit  Just one Radiator is as cheap as $20.
One nice feature to add  is a water thermometer kit.(with display) (some use a tank in the DVD bay (gone DVD) and has water temp gauge there)

Next if the GPU runs too hot is the water block kit. ( how this is done depends on your brand and model GPU card, and what it allows and what fits correctly) Best HS grease is SHIN Etsu.

One more for fun,  Note the flow meter (yellow impeller)

Good luck cooling your fast PC. (some need this bad, with 250+watt GPU and 140watt CPU .
The worst case for any GPU ever is 365watts (old) that must be expelled from just 1 GPU.

TOP PITFALLS fast short list: (give PC runs ok on old video card or base onboard iGPU (intel) BIOS screens dead is the only key symptoms...
  • Old cards do no work in new PCs with UEFI CLASS 3 BIOS,  and all PCs (turn key OEM) 2020. (Asus, you can buy what you want , unlike DELL or HP)
  • Wrong PSU, forgot you need 500watt (min)PSU to run this card. Or you PSU is 10 years old and the CAP's inside are  leaked out or dry and now dead (or weaker now)(good/bad, shorted or weak)!!!
  • The  1 or 2 AUX jacks on the new card are not connected to the PSU, you forgot to do that, oops. An ATI R9-380 needs 200watts just for itself.  (if you see 2 jacks AUX,both must be connected)
  • The BIOS settings not changed from iGPU to PCI-e/GPU .
  • The monitors video cable not connected to the right GPU jack. ( GPU card, VGA> DVI , > HDMI, DP , in that order if present some or all)
  • The the monitor decided to fail today, dangme. take a rope and hang  me.... (dang 10 year old CCFL black lamp tubes died or work only on odd Wednesdays)
  • The PC needs a hard reset.
  • The main motherboard, RTC Coin cell battery decided to fail today (5+ years old easy) Replace it  any time BIOS acts odd in ANY WAY at ALL. Or BIOS can not old dates. (MM/DD/YY)
  • You forgot step 1,  remove old card video driver in DEVICE MANAGER? before the swap?

version 6;  5-1-2019 ,  redux 1: