Warning signs of PC going to poop out?

[Theodore Donald Kiravatsos]

Last night, in the middle of a game...

BOOM! PC starts rebooting, with no warning. This has never happened to me before. Immediately, I worry about some virus or whatnot. After the restart, I get the grey Microsoft popup about how some program I hadn't heard of before has had a major error (I should have wrote it down), and then the PC crashes again. After second restart, I am able to save a couple documents to the flash drive, and initiate a virus scan. At that point, I took the PC offline by powering down the modem and router, and started up a virus scan.

Then I went to bed.

This morning, Computer Associates virus scan came back with the usual....zero undesirable things found or blocked or quarrantined or removed. Right now the PC appears to be working normally.

This leaves me with the question...do you suppose this was a warning of impending PC doom, or just an aberrant fart from within the guts of my PC? I should add that my PC is two and a half years old, and it is a Compaq Presario Cheapie.

I suppose it could still be a virus, but I am doubtful. I plan to back up more documents and stuff before visiting the Panda scan site to double-check. I would just like to hear any opinions as to what may be the culprit to an unannounced reboot, because if my PC's going to go, then it has to go, and if it's a virus, then IT has to go also.