LOL it figures. As I posted that "offhand I'm betting it's a laptop" thing I said to myself, "Idiot, that means it will be a desktop."
Do you happen to know if you have an onboard GPU or do you have a video card? I'd normally ask you to run CPUID
if you don't know, but you CAN'T because you aren't able to do anything. If you DO have a video card, you could try replacing it, or substituting it. I say substituting because you are posting here on a computer that isn't the one we are talking about. You tested your HDD on a different computer. If you that same computer has a video card, you could try using it in the dead machine and seeing if it works. I am focusing in on the GPU because I had the same problem. For some weird reason, when it happened, I could open my case, disconnect and reconnect my DVD Sata and DVD power and it would then be able to do a repair install. So I replaced my DVD (seems the obvious step, right?). Well after I replaced the DVD drive, it happened again. I replaced my GPU and haven't had a problem since. (That reminds me, I need to stick that dvd drive back in and see what happens.)
If you can't try another GPU have you tried a BIOS flash? If not I would say try that. I saw one instance where that fixed the problem.
Edited by DeathStalker, 18 April 2010 - 02:24 AM.