Computer Restarts Wierdly?

Hi,

Im on a WinXP SP2 with a NVidia 5200FX card and 512 mb ram

My comp was running pretty fine until it started restarting wierdly a couple of days ago.

This happens whenever i try to play a game or run a movie or some graphics related thing.

It also happens when nothing is running.

It looks as if the power went of and the comp starts again.

I then removed my graphics card and tried running the comp but the problem persisted.

All Fans are running fine and there are no wierd noises as far as I can hear…

Please tell me what can be the problem.

Thanks