Install something? Delete something?
If not, you may try system restore (pick one that created before your problem exist)
But, Powerdown can also be caused by:
Bad Memory (ram)
Dying power supply
Burnout Motherboard part, etc.
I have powerdown problems. You know, while I'm doing things on the PC, it suddenly shuts off (Not reboot, I still have to push the button to open). It happened without a reason before 3 days, and I still cant fix it. I tried to disable the automatic shutdowns. I formated. I did all the things that a related web-page was saying. But still its not fixed :(. The big problem is that, when it powerdowns, and I try to reboot, it always powerdowns during the reboot. Sometimes before even the monitor opens, sometimes 10secs after that, sometimes when the Windows XP logo appears, sometimes when a "beep" sound plays...
Please help me.