Odd problem with certain games.

When I play call of duty 4 and counterstrike source, after ive been playing for about 5-10 minutes, my computer will flash something that looks like blue screen of death, and then restart. I can play bioshock and crysis maxed out for hours straight without this problem, it only happens in these games.

So far i've tried this:
reinstalling the games multiple times (i even used a different disc once)
messing with the graphics settings on games
closing all background programs

computer specs: custom built
nvidia 8800gt
3.0ghz dualcore processor
Asus p5n-e SLI mobo
2gigs of ddr2800ghz ram
running windows XP

PLEASE anybody who has an idea of what might be happening let me know.