Usually a "general protection fault" is a generic way for windows to say "oh shit, something went wrong" I would suspect it to be software related, but the heat theory is valid. Easy way to test - take the sides and/or top of the case off. If it's heat related then it won't recur with full ventilation. Assuming that the processor has a good enough fan/heatsink combo is fairly safe, usually if that's the problem you'll only get a few minutes of use before it craps.

But that doesn't sound like hardware. Typically when that's the problem it isn't nice enough to give you an error, it just stops working. Try re-installing your device drivers with the newest version you can find. Then you may have to reinstall windows....ugly stuff.

If it's not crashing during regular use (web, email, etc) then I would look at video card drivers, maybe even the card itself. Bad video cards can cause all kinds of strange shit to happen. Again, look into software first.