Computer switches off on its own

my computer switches off on its own.

dunno whats up with it think maybe it could be the power supply..

also keep on getting blue screen of death with a 9c hardware error.
bit stuck as dont know a lot about the workings of a pc i have recently instaled a nvidia 6600le gfx card so might be that.

any help or advice on what the problem could be would be much aprecited..

my system specs
amd athlon dual core 64x2 3800+
nvidia 6600le gfx card
creative audigy 2zs soundcard
4x 512mb ram sticks
gigabyte
idna geforce series mobo gforce 6100 nforce 430 chipset
maxtor 200 gb hard drive
Lg 16x dvd drive
dunno what the power supply is it came with the case

thanks

The Nvidia drivers probably corrupted the registry... Try performing an XP repair. Here are the instructions:

http://www.geekstogo.com/forum/How-to-repair-Windows-XP-t138.html