It's not cognizant so it has to be. At least, his PC shouldn't be cognizant.
Oh and I curse you for that signature, Turan. It's very distracting because every time I see it, I stop and muse on just how clever it is. ;p It hadn't actually struck me how clever it was spoken but reading it ...
I'm going to go with I/O failiure then, followed by overheating at a distance. Overheating might be happening but you'd be seeing other things, like weird cursor glitches and at least some artefacts somewhere, or you'd crash if you tried to run WinAMP with visualizations for example.
I/O refers to input/output, basically this could be the IDE controller, the motherboard, the cables or the drives themselves that're the source of the IDE issue. You could swap in some new hard disks but if it's the motheboard or the controller then you'd only ruin those too. I'd suggest trying a new motherboard before anything else. Oh and check your in-case CPU/mobo temp, just in case.
I'd say, build. I know there's a lot to be said for purchased PCs but you'll care more about a PC you've pieced together with your own two-hands rather than one you've snatched from under the armpits of Babylonia.
That's just my personal opinion though.
It isn't easy. I will be on hand to offer advice and aid if you need it. You can stop by the #ace channel at irc.datavortex.com (I think?) any time you like. I'll be happy to walk you through the procedure and offer whatever advice I can along the way.
It's just much more rewarding.
Oh and what's happened to your current PC either sounds like an I/O failiure (nothing would be working if it was your CPU, trust me on this), it's having trouble reading things off your hard-disk. That could be caused by general hardware failiure or ... dun-dun-dun malicious software. Either sloppily coded or a virus.
When you start your next PC, go open-source. Use Windows if you have to but make sure it's XP Professional (the most benign version). Then make sure all of your applications are open-source, Firefox is a good start. Never, ever trust freeware. In fact, I strongly recommend you always look on freeware with a suspicious eye. Freeware is far less trustworthy than even software you'd buy off the shelf. Furthermore, you'll feel better about having genuinely Free stuff on your system, I'm sure. With that kind of software, no one can take it away from you with some form of shitty license, it's yours.
And if you pick the right software by efficiency-obsessed groups, your PC will love you for it too.