boom

i believe its the power supply, its not a virus as we have full updates and a new hdd and win xp.i get no warning at all. its like the power been turned on and off at the mains constantly.sometimes its fine then turn on and off about 5/10 times of part way through doing something.

i can`t seem to get my girlfriends pc to run stable. it used to restart constantly as if there was a power cut, i virus scanned but no errors.sometimes not able to complete the scan as the pc would randomly restart this could happen 20 times in the space of about ten minutes. we then bought a new HDD and a new version of windows xp pro,all was well with the installation,but recently it as started doing the same thing,only other software i have included is for her ipod.i have never encountered this problem before and its extreamly difficult to use for work due to constant reboot.windows gives no warning just reboots. any help would be great. thanks