Computer locks up completely when gaming
Whenever I play ANY of my games (Left 4 Dead, Call of Duty 4, and others) they will eventually freeze. When they freeze my entire computer will lock up and I will not be able to ALT+TAB out or CTRL+ALT+DLT either. The freezes don't happen every time I play, but sometimes my computer will freeze multiple times per day which is a big headache with some online games.
My specs are: Intel Core i7 920 processor, EVGA Geforce GTX 260 graphics card, 3 sticks of DDR3 2GB RAM, 650 Watt Corsair PSU, ASUS P6T motherboard, and two 7200 rpm 500GB harddrives. I've been using 32-Bit Vista Business and will be upgrading to 64-Bit Windows 7 once my copy arrives in the mail. Also, everything is running at stock speeds too.
At first I thought my problem was with my GPU, but the temperature is normal during gaming (70 Celsius) and haven't had any artifacting so I doubt that would be a problem. Then, I ran MEMTEST 86+ version 4.0 for a few hours to test my RAM which returned no errors. I'm thinking it may be a PSU problem, but I took a multimeter to my PSU and motherboard/cpu connections to test the voltages and they were all in the normal range. I've used some other diagnostic programs too, such as OCCT and SiSoftware Sandra Lite, but I have found no compelling evidence to replace any certain component. At this point I am not sure what to do aside waiting to install Windows 7 and see how my computer functions then.