Computer keeps restarting

[nomieputre]

my computer was working fine, i downloaded pcCillin 2007 trial version...the next thing i know...my computer starts restarting by itself. i have reformatted windows 2 times now, and it keeps on restarting. i tried installing the latest video driver, but it only made problems worst...this is a new computer (2 months old). I reformatted the entire computer 2 days ago and have barely touched my computer since...Today i got the RPC doom virus even though i am protected by Norton Antivirus and Windows firewall. It isnt the temperature of my comp either...it reads at 56 degrees celcius...anyone have any ideas??
it has:
250 gig harddrive
1 gig ram
256 dedicated memory (Radeon X1300 series)
wireless internet
PCI Expresss Motherboard

 

[beef_jerky4104]

I think you its your power supply. If you built the computer yourself and used a free with case PSU then that is likely the problem.

 

[Soap]

i agree with beef_jerky. do you have a spare power supply or a 2nd machine you can get a psu from? or check what voltage the psu is actually producing?