After a minute or two from when windows loads my computer randomly shuts down. I have a home built PC with windows XP and have never had any problems with it until recently. Then while installing a windows update, (only thing that was running at the time) my computer reboots. After a few times it is still happening, so I boot up in safe mode and system restore, but for some reason I have no system restore points before the problem. I have booted in safe mode and run a Kaspersky 2005 scan and a stopzilla scan and found nothing. Is there anything I can do or will I have to format? 
