computer turning on anf off by itself?

Find your XP cd or Vista DVD and get into Recovery console. When you get the black screen with the C:> prompt type FIXBOOT and confirm if you must. When it finishes type FIXMBR and confirm again. When it finishes you may type EXIT, although it may be prudent to run CHKDSK c: /s /f first. This will look for hard drive errors and the /s /f options will try to fix them.

After all this you should be able to at least get into safe mode and finish whatever you were doing. I hope that you were updating your drivers because it seems that either one of them was crashing or your pc is overheating.

Should none of the above work then a likely culprit is overheating. Find out by running the pc with the lid or side open and checking the fans. If they're working then they should be going so fast that you cannot see the blades. Use a soft brush like a paintbrush to brush dust and dirt off microchips. If there is dust under fans then unscrew the fans one at a time, brush the dust off and screw them back down (This is very likely to be necessary on the processor fan, so don't be afraid to brush off that heatsink). Remember to check all fans and blow dust off them WHILE HOLDING THE BLADES STILL WITH A PENCIL (you could damage the blades), including case fan, motherboard or system fan, processor fan, graphics card fan and any other fans not already mentioned. You could install an application like SpeedFan so that you could monitor the fans through Windows with the case closed.

*Dust is the biggest cause of overheating and crashing.*

Carly
August 2009