hi everyone I built my computer about 6 months again. And Just recently it will reboot will Im playing COD4 not at the same time, like 20 mins then 1 hour then sometimes not at all. Please help

Specs
CPU-Intel Core 2 Quad Q6600 at 2.8 GHz Sunbeam TuniQ tower 10 CPU heatsink
GPU-8800 GTS (G92) 512MB 256-bit GDDR3 PCI Express 2.0 X16 Core Clock 678MHz memory clock 1944 MHz (3 months old)
Ram-Corsair XMS2 2GB (2X1) 240 pin DDR2 675 (3 months old)
DVD burner-LG Lightscribe 22X IDE
Motherboard-680i LT
Hard drive- 160 GB 3.5" SATA 7200 RPM
Case-Thermale M9- 3-120 mm case fans 1-80mm.
PSU-650watts Antec

Temps CPU 32 27 34 26 GPU 50

Windows XP sp2

Everything Is like new Computer cleaned every week Doesnt run at night. The temps are always really low and It never reboots while doing other things just when Im playing a game The Event viewer under system looks fine, i cant figure out what is wrong its really annoying playing a game and then the system reboots please help thank you

Set it to stock. Its a 680i get used to it.

Sounds like a vga card issue to me. Have you updated to the latest Nvidia drivers?
If so, have you tried a beta version?

To try to separate out the vga card as an issue, run Prime95 long enough to be certain that the cpu and memory are ok.

The 678mhz clock is a bit higher than the reference clock. What happens if you underclock the card. If that fixes the issue, you might have to return the card, it should still be under warranty.

first are you overlocking? set it to stock and see if it still crashes in game.

also you can't rule out temperature by checking idle temperature it only crashes in game so check in game temperature but first try setting it to stock values. video card i wouldn't worry about yet if it came from the factory overclocked.

I had issues at one time on my systems, if I didn't have an exhaust fan mounted under my PSU, it seemed like I got more lockups. Try mounting a good high flow at least 80mm fan underneath where your psu is and see if that helps. I don't think PSU is your problem. What it kinda sounds like is you are having heat build up over time.

i had the same problem when i had installed some approved ram for my mobo,random crashes but only when playing games or anything that seemed to access high memory,so i wound up installing better quality high performance ram and all my problems went away,and the installed ram is not on the qvl list either..go figure..
the other item i would like to bring attention to is the thermal paste,hopefully you did not put too much on,as this would produce the kind of results that you are getting,you only need enough to fill the micro holes between the two surfaces,cpu/cooler,,and you do have an excellent cooler..:> )

Thank you everyone for your advice. i set all My settings back to factory settings and it has not happened yet The first guy must be right about the mobo. Thanks again