EN8800GT Game Restart

I purchased an ASUS EN8800GT, (along with a new mobo and RAM) and installed it in my computer. Everythings been fine until I try to run a game, in which I get a blue screen saying my computer has been shut down to prevent damage, then it gets rebooted. I get an error message:

page_fault_in_nonpaged_area

I have downloaded and installed the video drivers, as well as installed the ones that came with the motherboard.

My system is:
Intel Pentium 4 3Ghz
Windows XP Home
Kingston DDR2 1GB
Asus EN8800GT
Gigabyte P31-DS3L
400W PSU

Is this a driver issue? Overheating? PSU? Has anyone encountered this problem before and got it fixed?

You may need to upgrade your power supply

Hmm thats what I suspected...

Anything you could recommend me? Something that would need to power the above system w/core 2 duo, 2GB RAM, etc as I'm upgrading gradually.