Having Problems With Moh (crashing)

[sickshooter]

I have xp home and havnt changed to pro! I can load up moh perfectly, browse servers and join them, but then from which i have spawned to max about 30 mins my computer crashes. i cannot switch to the desktop using either Alt+Tab or Alt+F4. i cannot enter the task manager using Ctrl+Alt+Del. the only choice i have is to press the reset button on my tower. Now this may be an over heating problem or the fact that i have the latest nvidia driver. here are my system specs just incase u need!

Operating System: Windows XP Home Edition (5.1, Build 2600) Service Pack 2 (2600.xpsp_sp2_gdr.050301-1519)
BIOS: Default System BIOS
Processor: AMD Athlon(tm) XP 1800+, MMX, 3DNow, ~1.5GHz
Memory: 512MB RAM
DirectX Version: DirectX 9.0c (4.09.0000.0904)
Card name: NVIDIA GeForce2 MX/MX 400
Chip type: GeForce2 MX/MX 400
Display Memory: 64.0 MB