OP: Counter-question time. Do you ever get oddly named or sized files?
Do you ever get STOP errors?
And if so,
Do you promise to write down the error codes of any future STOP errors?
g-money wrote...
@Tegumi: You're right that viruses attack the software, but I've heard cases of viruses forcing the computer to shut down and reboot or something of the sort. This sudden shut down does sound like a hard drive issue, and I know that cases of overheating, the hard drive has a failsafe system that shuts down by itself to protect it. But if that happened, nothing else should've been affected unless the hardware was damaged to the point that it affected the software. Then again, I don't think we know enough information to diagnose and troubleshoot this case.
The computer "shutting down due to a virus" is actually about the sasser (and variant) worm, which exploited an Local Security Authority Subsystem Service (LSASS, hence the worm's name) vulnerability, crashing the LSASS. This would cause the affected system to display a brief information message and countdown and then shut down on itself, because a termination of the LSASS and ensuing loss of security policies triggers an auto-shut-down.
Symptoms given by original poster are completely different from this.