HaloMods "Classic" Read-only Archive

Ok I recently ghosted my PC because it was messy and I reinstalled CE and all my games then now everytime i go play online for a while my pc restarts all of a sudden... it has happened with Halo, Halo CE, and Counter-Strike source.. just restarts all of a sudden. The first time it happened is when i opened some ports for winmx and then i started winmx for a while then it restarted and from there it just kept restarting when playing online, I closed the ports but it still happens dunno why... PLZ HELP ITS ANNOYING

AMD Athlon 1GHz
512mb ram DDR
GeForce4 Ti4200
Windows XP Pro SP1

Probably a virus...I had the same problem, but this is my bad computer, so I don't really care.

My computer also turns itself on overnight (not kidding), so I just turn off the power supply.

O.o

No, I used to have this EXACT same problem. Only thing that worked was to Format and reinstall Windows.