One other thing-- I don't think this was made clear enough in my earlier post. Most computers use ACPI, and the defaults for this are pretty common. The standard option for powerfalure is 'reboot', the most common option for overheating is to 'turn off'
This actually has interesting implications:
- If it reboots it could be a fault in the PSU, the mobo, or to a far lesser degree bad ram or a bad (video) driver. (Mind you the latter two are 'free' to test.) A faulty PSU or Mobo will look like a powerfalure in most cases.
- If it goes off and stays off it's probably heat. (And you'll probably get a nasty warning by just turning it back on.)
- If it hardlocks it could be a bad (probably video) driver or anything else poking the lowlest level bits of your OS. Then again that could also be bad ram, or pretty much any bit of hardware. Checking your firmware and BIOS is a smart plan here as well.
This all assumes you are virus and spyware free.
Anyway, I just wanted to throw that out there.