Probably a lost cause, but I thought I'd ask before I start replacing hardware.
I have a desktop that's been boxed up for a while, and when I set it back up I wasn't getting any video output. I pulled out the PCIE card and cleared the CMOS, then it started working fine with the onboard GPU. I assumed the card was bad, since I had problems with that model in the past. Then after a day or two the system locked up and I had to do a hard shutdown. Now I'm not getting any video from the onboard either. I cleared CMOS again, tried with and without the card in place, nothing. When I power up the CPU fan spins, but I don't see any other signs of life. The hard drive access light doesn't seem to come on either, which makes me think that this is not just a video problem, but I'm not sure what BIOS does if it can't detect any video device.
EDIT: Interesting development. At Xantec's suggestion I disconnected everything, which worked. I then started reassembling it piece by piece, and I now have everything back together- even the video card and other peripherals that were not attached before- and it's working fine. I'm typing from it right now. I have no idea what the problem could have been, but since I didn't narrow it down to anything I'm afraid it will just happen again.