Crashing while Gaming, please help

ok well i have had this strange problem for a while now, and i cannot stand it anymore.

when i first build my computer and got crysis, while playing, at random my computer would shut off. now this would happen 5 minutes in, 3 hours in, or sometimes not a all.. completely random.

now i had always thought, this is crysis its buggy.. bla bla so i let it go.. it happened about once a month with cod4.. so i didnt make a big deal of that.

but now i got cod5 yesterday, and it crashes within 10 minutes.

the interesting thing is.. i play the witcher, farcry 2, and fallout without any hitches.. theyve never crashed on me through extensive play, 5hrs + on fallout 3 at a time..

i upgrade my graphics card drivers and motherboard whenever a new one comes out. i have reformatted by comp 3 times now due to unrelated things and the problem persists.

my specs - antec 900 case, all fans highest settings, cpu runs at around 30 c idle and mobo 40-50. ( can check again if issue is important)

SLI EVGA 9800gtx's with nvidia 180.48 drivers

EVGA Nvidia 780I sli Motherboad with nvidia 20.08 drivers and 6.03 system drivers

Q9300 @ stock settings with core contact freezer cooler @ highest fan speed

2 western digital 500 gig HD's in Raid 0

Creative soundblaster fatality pro soundcard with latest drivers

4 gigs of corsair ram ( 2 sticks)

OCZ 680 watt PSU

Vista 64 bit home premium