Graphics crash

Hey all,

I have a PC with the following specs

ASUS P5L 1394
2G RAM
GeForce 7600GS 512MB
X-Fi Fatal1ty
Dual Core 6400 2.13Ghz
Windows XP Home

The problem is, that when I play games the game freezes for a couple of seconds and the returns. Sometimes the sound and the graphics freeze (Godfather) and other times just the graphics and the sound continues (Flight simulator X). I have downloaded all the latest drivers for hardware and all updates for software.
I had Vista installed a couple of weeks ago and the problem was the same, so I don't think it is a problem with the OS.

Any ideas on what could be causing this problem? It has got to the point that I can't play games anymore.

Thanks in advance.