How does  PCI work and  plug and play (PnP).   Redux1                             See related page Drivers. 
See the short answer here:
(below is all the sordid reasons to fail and cures)

You are hear for only 2 reasons, you loaded  new OS or upgraded and chips are now dead,(or weak) or the kids were playing with drivers and killed them dead.
I can the results of that act above, slamming the OS.
By: Deadpool.  

 There are 2 ways to sniff  chips to learn what they really are :
  1. Open the casings and read the names and number off the chip (the Realtek ethernet chip is just behind its port) Chips with heat sinks no possible or painful.
  2. SCAN it (sniff it ) see my 10 ways list below. My top choice now is Hwinfo32.exe.

Plug and Play (PnP is a process that both Window and newer LINUX both do , to detect, and discover what chips  are in your PC and to find a correct matching driver to your OS (OS, means your "Operating System", and please avoid XP)
Learn that each chip (major functions like video, USB and networking ) all have internal device identification storages locations inside those chip, that the PC can query (commands do that, and is called enumeration by MS geeks)
These commands are PCI commands. (that happen at BIOS and OS levels both)

Here is a crude and  is a serial  simple PnP flow chart:

  • BIOS scans some devices  (It for sure sees your Video chip and some USB ports to run say a keyboard to operate BIOS screens)
  • BIOS then passes these scan  facts to the OS next (via a shared memory location)
  • The OS boots and then runs a deep PCI PnP scan, it scans for many things, and misses nothing, SEE  this nice tool.  See how enumeration scans work !!! at WIKI? This does repeat if you plug in a new USB device.
  • This scan searches deep, then repeats if you add or remove any USB devices. 
  • Then with the 2 codes (and version codes) VEN and DEV,  are seen it is recorded and is used next by the OS. VEN means Vendor or Manufactures name, like code 8086 =
  • THE OS then looks in the local OS driver cache  to match those 2 codes above to a matching OS specific Device driver in the driver store. (if running XP service pack 3, SP3, more drivers are there now, added)
  • If the local driver is not found (no match) the OS finds an open internet connection, via wifi or LAN  ports.   (if not connected now, all hope is lost , halt here and see last line below) (try Ethernet first; never wifi)
  • If you have W10 it can find drivers on you subnet other PCs at home or a business, if that feature was  turned ON by you , or finds them on your neighbors PC, again if turned on by them, . If fail  we go to the next step/
  • If not found yet, the OS then goes to  MS driver servers, and  catalogs, MS may block this on XP or VISTA or older, now or soon. (for sure call in phone helps dead on those 2 OS)
  • If  the OS found the driver online at MS , matching the 2 codes, then the OS loads said driver and all is well (the magic of PnP)
  • If it fails,?
  • The OS marks the DEVICES (in device manager) as RED, YELLOW or UNKNOWN, Thus ends PnP until say you plug in a new device, or reboot  with say  a new USB device.
  • Learn that Unknown, still has 2 codes of you were to look,  Unknown means "NO MATCH-UP" or your web connectors are dead, a microsoft server is down, or the device really is not supported by MS.

PnP fails for only 3 reasons. (I will  assume your PC is not infected and the OS is freshly loaded)
  1. The driver is not found local driver cache (in C: windows folders)
  2. The driver does not exist for any reason in the Microsoft Driver server catalogs, online (or your not online?)  (MS does have vast drivers in there online update servers seen here)
  3. The driver does not  exist (say trying to run W7/8/10 and your chip that fails, due to the maker of said chip ending support or never made a driver for it after 2002. (vast makers fall in this catagory, for chip older than 2010 VAST chips)
If not online?, read this.

Things you can do to make this more easy (PnP fails and you are web connected and failed) are here.
  1. Learn what chip fails, then what are the VEN and DEV codes using Windows Device manager. (or if its marked UNKNOWN use the PCIsniffer3.)
  2. Look them up in the PCI data base to see what the true names are and true chip numbers.
  3. Look them up in the MS data base manually.
  4. One can in vast cases just look at the object that fails with your  eyeballs,  read the makers name and the chip number on it. (video cards, Network cards of any kind, USB devices of any kind and more) looking works 99% of the time. (unless say mobo chips with heat sinks covering names)

All 9 WAYS to sniff chips is below: (10 ways counting eyeballs on to top of physical chips)  I have tested them all.
The hard way with Device manager.(DM)
Or using GREAT APP's.

This next section  below shows how to scan and detect hardware, just like BIOS PnP does. (call PCI scans) BIOS PnP evolved fast after 1994 seen this Intel document.
The vast number of ways to know what hardware is there, are:
  1. Run HwInfo32.exe (portable version free) Best in class !
  2. Ask Windows Device manager  it may show it, and you can see it device properties IDs   (the DM may flag it as Unknown, RED or Yellow marked (errors) Use the DM way to learn chips.
  3. You open case and read the chip failing name of  its lid. (abvious to any well trained technician but can be impossible if the device is heatsink capped)
  4. You run the sniffer3 program to find its true PnP ID. ( a free program it is) and all the others listed below,(ways and means).
  5. You can give HP your full service tag data and they will tell you what is inside your PC the day it was sold, (warning : it can have 3 GPU chips, 6 network chips and 3 sound chips sold in 1 series, but has a unique  XXXXX#ABA partnumber there on that sticker.
  6. Boot a Linux Ubuntu 16 (in demo try me mode)  and ask it to enumerate all PCI devices  using the command line command lspci , to linux OS with full deep scan switches turned on.
  7. Or use the fabulous Windows 32/64bit version of the Linux LSPCI , like this example here LSPCI -nn -v  and see this.( this is my Ethernet port, so we can get the internet working and plug and play, this is usually a 1st step on any PC)
  8.  I never run SPECCY as is  full of malware even from, makers home pages,  that can be turned off "customize", but tell me why trust anything that is preloaded with malware, they do not earn my trust, sorry.  THAT IS MY OPINION!
  9. The PCI-Z works great too, and is a GUI under Windows, and is portable application. (nice) My guess the most easy of them all and 100% Safe and Free.
Once you learned VEN code and DEV code we then...

Good links:
Microsoft drivers servers can be examined for drivers.
Using the direct MS look up manually.

Next up is?  PCI, it's a standard for asking chips who they are. (chip info scans)
PnP also finds printers, scanners, Displays, keyboards, mice , and a zillion and one , USB devices. (PnP job is to find all devices that need to work here)

How to scan and sniff out , PCI identifications from chips.
#1 is Hwinfo32.exe (portable)  See me click things below.  This is Z270prime system.

The below I clicked (network) It is the Ethernet chip, and get the VEN = code and the DEV= code if this chip is dead or weak.

More examples of dead chips and how to find the codes and then the matching OS driver to it.

Rule 1 on scans, if say your USB2 port is dead, the internal camera will be both dead and invisible to scans ( like trying to see in to a room and can't but the door is locked, USB door, if you get my drift)

 First may I say if you can't use Ethernet (you own what I call potato chip thin notebooks,  (I hate them) then get wifi working first, or PnP will be 1/2 dead or worse.
There is cure for above, pain, a Ethernet (LAN) USB dongle, buy one for those days, WIFI is hopeless. (as can be)

Well, I run this  program called PCI scan,  that finds all chips in any PC.( the newest version is even better, and finds my wifi chip fast)
I use PCIsniffer v3, by Milray, direct. (< link busted )Please us this  link instead at Major GEEKs.

One Example only (there are 20million drivers now )
In this case, my WIFI chip was dead and Device Manager (DM) showed it missing, (or unknown or marked RED or YELLOW) In some cases using a MS install disk (bad) on a HP PC, you can see 10 things in DM , as Unknown, like the fingerprint reader.
I fiddle about in this Sniffer engine, and find my chip, easy as apple pie. (Ethernet first then wifi last)
In DM you see this.,  See details,  even a dead chip has this, even UNKNOWN (unknown only means I can not find a match , the OS can't but you can) dig?  Click details, read the numbers write them down, now.
See VEN,  Ven means vendor,  or maker, can by INTEL or RealTek and many others, thing of VEN as  house address and then DEV as ROOM in that house.  DEV is for Device, that they made , in this case Network chip.
I clicked properties in Devic manager then clicked Details,  and last clicked Hardware Ids (scroller)

If for some reason VEN and DEV can't be found. (try to know fixing one, bad driver, will unmask more chips (some are cascaded is why)
PCISniffer 3:
(love it I do) I have it on boot mini CD and on STICK USB.

My INTEL Ethernet card  is on the left B0 but B68 (say buss 68)  Is my WIFI chip and is an  Intel (8086) chip and is code 4239h, if I use the database scan , you look it up that way.
If the Device Manager shows Unknown and you want the Vendor code and Device codes, nothing works better.
To use this program, boot to CD  (or stick) open all left sides items so you see all B0:xxxxxxxxx items, the click each and see what it is at the top of the screen , in this case the  Centrino N6200 wifi chip, click Ethernet on left side, to see it.

The sniffer can even find this card,. Windows 95 PCI card that works.
After you find what chip is dead, (even Device manager told you it was dead) but you found it using the SNIFFER,  then see my DRIVERS page next.
Once we get this far with a makers name and Device name,
We then go to HP and get it or from the actual maker LAST,  (If  video GPU chip go to Nvidia or AMD/ATI home page for drivers and get now)
If not video, go to HP and get your driver there, first. or if not supported at HP then at the chip makers site, if still in business. (google" Realtek home") or Intel home, or Intel drivers. like that, easy no? but not if they left this business.

Examples of How to find important drivers:
Complaint stated as , I can not set full resolution on my LCD screen (not caused by using old 800x600 20 year old screens)
The video driver is stuck in MS limp mode, is the cause.
Here are some examples at Nvidia.
  •  Like old Nvidia, Nforce chips
  • Here is the Nvidia trick , in this page, set the first toggle box line to LEGACY and see all drivers for all OS there, on nFORCE (they hid it deep with this trick)
  Do know that W7 was the last OS supported for most of these, old Nforce chips. But might work ! Try it, see for  your self, what works.  I offer this example to show how hard this page is to navigate.
This page works for old Glue chips and GPUs.
Case in point, if the Ethernet chip driver is missing, here it be.!
If you need old Intel drivers, go to home. and get them.
Most old video cards and chips are not supported now, and not for W10.
Need AMD/ATI GPU support go there.
I show here examples of on top makers above and the 2 links below show the top makers and the dead makers.

The top chip makers are here today.

See a   list of old defunct chip makers,

The fastest cure, after PnP failures is to let PnP find it on the internet, "BE CONNECTED"
The site has all my drivers,  I then load them all and now it works great. (in the correct order , I do that) Older that 10 years, last model made , HP support ends.
Lets say you are trying to buck the system and run a newer OS on your old PC, that does not support, well you get to do all this the the long hard way... (It was your choice, bucking the HP system of full support, Why do that ?, I DO but I know how to...)

CURE 1:    (worst case in networking)
I will assume below that HP no longer provides support nor the correct drivers now, over 10 years old PC that is what happens.

The natural PnP way fails  , Windows boots but can not find a driver, key to making something important to you work properly.
The natural way only works say 10% of the time with no internet connected, try the ETHERNET cable first with CAT5/6 cable to your router.
Does PnP work now, it should but does not,  Ok you found out the ethernet and wifi are dead, lets get Ethernet working first, after all it's the most easy way to get on the web, and to get updates or downloads of any kind.
You then go to Device manager (in control panel) as see in the photo below.
Then you click the network line and see both chips are dead, both wifi and Ethernet.  (Windows screens show, "unknown, RED or Yellow" flagged as bad)
(Microsoft Windows, click Control Panel then click device manager, then click your chip and right click properties, tab Details, last pick device tab and then roll Property to Hardware Ids (means hardware identification in ENGLISH)
This code here are the PCI codes. for this CHIP.  Knowing these codes can make finding a correct driver 10 times more easy.
VEN means VENDOR, (maker, manufacture)
DEV means DEVICE ( a chip) the you want to work properly.
The blue highlighted line of data.  VEN =Realtek  Dev= 8168 means RTL8168E / RTL8111F

Write down the line 2.

There are 2  kinds, USB and PCI.    USB looks like this.  USB\VID_262A&PID_9217&MI_01  (my DAC3 sound board)
Intel ID is 8086, named after the first real PC chip. (8088 was crippled)
Next go  here at link below, on a good PC and using the above line 2, find your chip in this data base,  to see the real name of the chip, for later usage if the MS lookup search fails, seen in the next section below.
Use the database tables and look them UP now, , after you  scan , your PC and learn VEN/DEV codes seen below.  (A good place to see links to PC ID repositories is here)

The above data bases convert the codes to real makers names. and model numbers of chips.
The above 10EC chip  is a RTL8168E, Ethernet chip. (wired networks)
We could go to and get the driver from them, now that we know the makers true name and chip name.

But first we look at Microsofts solutions next.  Using the VEN and DEV codes as Microsoft search below makes for faster and more accurate look up of your driver.

Microsoft's  manual  driver search engine: (It seems to be getting better and smarter today)
Find any PC that is on line, on the web first, not your dead PC or dead network chips) (new)  check out this very very old S3 card.
I am typing now on a PC with   this NIC chip  here:   PCI\VEN_10EC&DEV_8168
Best is to search MS using  just that line above. (or YOUR  line 1 in DM)
Next best is search, Realtek and see 500 chips/drivers there.  (hard no?)
or type Realtek, RTL8168
I get only 4 pages of drivers now. So pick your OS and then newest one.
If I used the full line 1 codes at MS I get this more exact response.
You can even search with just a simple name there, like S3 (now defunct) or 3com, see near zero support for most of 3com network cards, (HP owns them now) or search Intel and see 1000 of pages.

See a  
list of old defunct chip makers, this list  shows vast chips not made now, in fact most are not made now and most are not supported now , made from 1981 to 2001, vast chips not supported. ( Sorry drivers must exist first)
Think like this, how can  a dead company and the engineers now working at another company make a driver for  this dead chip line,  the answer is ,impossible.
Learn now that even some chip ended at XP or ended at VISTA. (and for sure older , eg: Windows 95 is dead to the max as are its  old chips)
As time marches on,  drivers, die.  (PnP is not magic, there must be a working driver some where on earth)

Here is me searching now, at MS.

See me doing a (VEN only search) almost 1000 chips by Nvidia at (MS).

Now for fun lets do Intel code 8086:

MS LIMITS: (and more examples of what you can do or not do)
Seems MS limits pages to 40, and 1000 devices per search, so the Intel pages are truncated. (that's ok  ,narrow your searches)
The best way is to learn the DEV code for your PC, and this web site (once you learn yours codes in DM look them up here)
The depth seems to be back to 2001 only. PCI BRIDGE
Searching for the Intel ICH9 82801 is not easy , and does not work using its correct , DEV code , MS indexs the GLUE chips by class, and series as
seen here.
If I play around with the MS search I also learned it allows you to search a simple name  like Intel or VEN_xxxx  but has no fuzzy logic.

That means VEN = 8086 fails.  and DEV (space or coma fails too) it must be exactly like this PCI\VEN_8086  (but the PCI\ is not needed)  I can search just  VEN_8086 .  (I am sure it's just SQL searches front ended on a we page)
No wild cards allowed, here, ? or * or even a space (VEN 8086) only VEN_8086 works (underscore character here) but Intel works by itself,
As does intel 82

Here we see XP is still present at MS DRIVER servers, with exceptions or live PNP fails online and you go here and find XP using manual searching as seen here.

I have learned that some XP support is still there but fails 1/2 the time and less every month later. (MS is silent on this topic, drivers and when they become deleted there little secret) but you can look and see what's there an not at any time.
I tested many old 2001 PCs with boxes full of old PCI cards and most failed, but not all. 2017 tests.  (live testing , ethernet up and working ,tests)  
The chip older than 2001 are very problematic, unless the chip maker has drivers, one such company is
Maybe the MS secret is they delete files over 18 years old. (or 16 and are late doing so... heheheheheh)
As you can see drivers there are a moving target in time , hint , get them while you still can.

LSPCI command, magic. (steps)  (all binary fails tested with the powerful shows 0/60 good.  (my example is Ethernet chip dead due to its driver missing or corrupted.)
Some great person ported Linux command to Windows, this is cute if you like command line , like me.
  1. Get the free utility  file here and put it in a folder here, C:\LSPCI  (that means create  the folder first)   This works so good, I have to pinch my self ! for sure with the --switches used!
  2. Then in the run box type cmd and right click cmd.exe and pick run as Administrator.
  3. The windows DOS like box opens.
  4. In that box, type CD \LSPCI   (the space after CD is manditory)
  5. In that folder is a zip file, so unzip it using windows or 7zip (best of best is 7zip)
  6. See LsPci.exe file this is  DOS utility, runs in command line only mode, don't be scared of it its just a utility tiny.
  7. Type LsPci -nn -v  (  there are 2 spaces there,  one after pci and one after nn,  this gives a great report on all chips and the secret PCI,  VEN and DEV codes, (vendor and device codes)
  8. If the Ethernet chip is dead, we get those 2 codes on paper.
  9. The go to Microsoft here and paste or type those codes here (on a working PC, one that has ethernet working)This is where Microsoft hides the drivers,  if you find yours, there, using and other working WEB PC, get it and load it onto the bad PC.
  10. Here is my example uising windows LSPci.exe (with the -nn -v switches)  So we would go to microsoft and fetch that ven:1043 dev:8432 driver, or get it from . Then the Ethernet port starts working, but do this on a working PC with internet first.

Or run this : PCI-Z

RECAP: all ways from Sunday to get DRIVERs not infected. This is my very short list of solutions that do work.
The correct order is , Natural, PnP let it find the driver automatically, if that fails get it at HP, if that fails get it at MS, and if missing there, try the chip makers web site and last look in the driver packs below.
Your upgraded the OS and not a chip is dead , and you run Hwinfo32 first to see what chip it really is, after all you PC maker may have used 3  to 5 differnt chips in one PC.
The chip is still dead even with the ethernet cable connected, so MS Plug and Play can do its job?

See my drivers page.

The biggest problems are , a PC over 10 years old , the makers drop  support (as HP does). ( and the web scalpers are born)
The 2nd big problem is , most motherboards have vast submodels, and the chips very greatly for sound, video,ethernet and wifi.  (that is why we use LSPCI to learn that, seen above)
The other pain (only MS pain) is the device manager may show your driver as Unknown or even 6 Unknown's,making it a pain to look all 6 up just to find out that Unknown #4 is in fact the Ethernet chip. (dang me). (use LSPCI instead or PCI-Z)
  1. The natural PnP works no issues, being online, now.  Like magic, until magic fails. then.... (fix the dead wifi or ethernet port first)
  2. PnP fails above, so get the driver direct from HP? . (when I say HP I really mean your OEM maker, ok?)
  3. Grab your original HP install media Matched to  YOUR PC and OS  and all you need is there, lost those?, (OS means Operating System, say Windows 10)
  4. If HP PC is 2006 and newer just , hammer the F11 key (1 second after power on) and recover the OS. (if the HDD is dead, this will not work) Many PCs have this and is called RECOVERY in your manual.
  5. HP (OEM) has no drivers then try the direct method.
  6. Get the driver now at MS servers direct manual method
  7. If your chip maker is still in business, (most are not, a historical fact) then get it from them,  like Intel, or AMD/ATI or Nvdia, or Realtek, Broadcom, and many more. (use the scanner )
  8. If not there, use the Driver packs next.
  9. One cure for XP is the Monster CD.  (or just extract what you want easy) a.k.a, driver packs. (tested by me for safe and no malware using
  10. Avoid Hacker sites, that lie, charge money and infect your pc with virus or malware, avoid this.
I always get the VEN code and DEV codes first then past them here, and find the driver at MS.
Realtek (for example) has 746 drivers, at Microsoft driver catalogs. PCI\VEN_10EC
How ever if it search using the full string below for ID's  I get 26 drivers.( or all OS that Microsoft supports now)

In my case the driver is at Microsoft or at  (in fact Realtek sends their driver to MS)

less is more.... I'm still editing this text.  adding more LSPCI type utilities, all  links are Virus free, malware free,  and are were scanned by me with  (a must action on anyones part running binaries)

ver.6 :::::::4-15-2017, revised 10-10-2018