How old is your powersupply? I don't know if its the problem but for my dad a solder joint broke loose and after so long of being turned on it would seperate and kill the system.
My old GForce card used to make my PC do that... it would get hot and simply shut the system down. I am not 100% certain that it was heat that caused it but I am 100% certain that it was my GForce. So, I dunno...
Make sure the fan on the Powersupply is not dead....usually that shutdown like that is the PS overheating. I have had many a fan bearing lockup and shut the whole thing down. Other parts can overheat and do the same thing. Also look in the powersaving features and make sure the dang thing is not set to hibernate.
well, on a whim i changed the screen saver just to see wassup. And I think that might have been it. I am still not sure but the computer has been on a while now. I have checked all the fans, and the PS seems to be ok. Although it is two years old. My computer pretty much spent the last year idling.
Wasn't the screen saver. And the answer is...
1 year of funk and dust. GROSS... anyway. guess I'll have to member to clean my comp out more often. But hey, I was away. sheesh. But it did bring my average processor temp down by about 20 Degrees C.