Sorry for the long message, but I'm hoping that the detail will help someone who has the expertise to see what the issue most likely is and let me know so I can take care of it.
Over the past 3 years as a serious hobby I've built several DIY PC's and rebuilt several laptops and several dozen off-lease PC's, but haven't seen this problem before so am looking for any help and advice from more experienced members of the community who might know what this is and what I should do to fix it...
I bought a used HP 8200 Elite SFF PC (Product Number: XL510AV) with a Windows 7 Pro COA, hooked it up to a KB/M and Monitor, turned it on and it booted to BIOS fine.
I then inserted a Windows 7 Pro full version CD to install the OS on a wiped and formatted hard drive and the initial phase of the install went fine. It was missing the network/ethernet driver so I went to another PC to get the 8200 Elite's driver for this model from the HP website and copied it to the 8200's desktop from a USB stick, then installed it, and it connected to the internet via the ethernet cable fine and downloaded a bunch of Windows updates.
I went ahead and installed the Windows updates, which all seemed to install fine and finished with the standard "reboot" request - which I went ahead and did like I've done many times before.
The 8200 shut down as expected, but when it started to reboot, instead of seeing the expected HP startup screen the screen was blank and the PSU fan started running faster/louder and faster/louder - so I pushed/held the power button and did a hard shutdown.
I thought the PSU might be bad and/or one or more RAM sticks might be bad, so I disconnected everything, took out the motehrboard battery, replaced the PSU and the RAM, replaced the motherboard battery, reconnected all the internal cables, hooked the 8200 back up to the KB/M & monitor & power cable and pushed the power button.
The PC then booted to Windows fine, but I did have to reinstall the HP (Intel) network/ethernet driver, then ran Windows update again. I went ahead and typed in the Windows COA and activated it at this point (and it activated just fine as expected), then I went ahead and installed the Windows updates that downloaded, which again all seemed to install fine and finished with the standard "reboot" request - which I went ahead and did.
The 8200 shut down again as expected, but, same as before, instead of seeing the expected HP startup screen the screen was blank and the PSU fan once again started running faster/louder and faster/louder - so again I pushed/held the power button and did a hard shutdown.
I disconnected the external calbes and also every power and data cable internally, took out the RAM took out the motherboard battery again, pushed/held the power button to drain residual power, replaced the motherboard battery and tried resetting the CMOS (not sure why, I just tried it...pushed the CMOS button for at least 5 seconds as advised on the HP web site), then reconnected everything and was going to boot again, but this time I noticed that the front panel power light on the front came on when I connected the power cord into the PSU at the rear of the PC and the same thing happened - the screen was blank and the PSU fan started running faster/louder and faster/louder - so I pushed/held the power button and did a hard shutdown.
At this point I'm not sure what to look at or do next.
Has anyone seen that type of problem before caused by things other than a bad PSU or RAM sticks?
Could it be a bad motherboard? What else can I do to diagnose that?
Could it be a power button or wiring intermittent short?
What else have any of you seen that could cause this sort of thing?
I thought about doing a complete disassemble all the way to a bare case to check every wire, cable, connection and screw; and then reassemble and try again; but if it's obvious to someone who's seen this before that it's a bad motherboard (and/or something(s) else?) then I'd like to save the time/trouble and just get a replacement HP 8200 SFF motherboard (and/or whatever) and install it.
On the reboot did you get to the windows splash at all? If so then the high fan could be a fail between windows boot and load of power management. Bad driver.
Can you force safe mode boot?
Will a diagnostic boot reliably? Can you always get cleanly into BIOS? points at Software problems.
Did you download and install chipset driver, etc from HP, or are you trusting windows install to get it right?
Guessing that after windows update system loaded new drivers and failed when booting with the drivers. Skip the ethernet driver. Skip the windows update. REinstall windows clean. Does the system reboot cleanly? If so add in enet driver, reboot. Still Clean? Now do windows update SUPPRESSING all device driver/hardware installs. Does the PC still work cleanly? Then goto HP and download the Win7 64 or 32 bit drivers for your PC.
<War story alert> I let win update load a driver for a wireless card. Hard hang. I could only get the system to reboot after physically removing the card. Installing driver from manufacturer of adapter instead of windows selected driver worked fine. Net win update doesn't always get it right.
No Windows splash screen on reboot after the Windows Update install session - only a blank screen and the psu fan started slow then increased in speed to a really high rpm, which is when I did the forced shutdown.
After the reboot problem and the forced shutdown, I tried a couple of boots and tried to get into BIOS each time with no luck...the PC was completely non-responsive.
I did the installs via Windows Update...the only driver I picked up and installed from HP site was the ethernet/network driver so I could connect to my ISP through my home network and start running Windows Update.
I'll give another go and disconnect all power and data cables inside and all external cables, take out the RAM, take out the mobo battery, remove and wipe the drive again; then reassemble and take another run at it...will try to boot to BIOS first after reassembly, then if that works I'll reinstall Windows and try your approach - install the network/ethernet driver, then run Windows Update and install only the non-driver updates; then reboot and go to the HP site and install the Windows 7 64 bit drivers from HP site.
Or should I just go to the HP site on another PC and download all the Windows 7 64bit drivers to a USB stick and just install them before I run Windows Update the first time (if I even get that far on this next attempt)?
If it doesn't boot to BIOS after the disassembly/reassembly what does that suggest...a corrupted BIOS? ...or particular short-list of hardware problems (from most to least likely)?
I'll get a chance to try again this weekend and let you know either way what happens.
I really appreciate the help, and the education - thanks again.