Sony Vaio freezing up

[sniper1371]

I've been having problems with my Sony Vaio VGN-AR605E laptop recently. Had it for a couple years no problems, switched from Vista to XP about a year ago, no problems there. Recently it's been freezing up whenever I try to play any game, or run a program (ex:Windows 7 upgrade adviser, Warcraft 3, Fallout 3). It also freezes up when I try to add music to my Itunes library. Sound still works and I can still move the cursor on screen. Nothing works but turning it off manually then turning it back on. Anyone have any suggestions? I'm at a loss.

Sony Vaio
XP Professional SP3
Intel Core 2 Duo @ 1.8 GHz
3 Gbs RAM
NVIDIA GeForce 8400M GT

I run rightmark CPU clock utility just to tweak power levels and keep the computer a little cooler, but that shouldn't be causing the problem.

Thanks!