I have just built a PC with the following specs: Rampage III Motherboard Intel i7 920 Processor Corsair dominator 4GB 2 x XFX GT250 (SLi) Coolermaster V8 CPU Cooler 2 x Western Digital Raptor (RAIDED) Cosmos Pure Black Gaming case When playing high intense games the PC crashes. The screen goes black and I can hear the game still in the background, but its in a weird loop. The only way is to power off the PC. I was originally using both cards in SLi, but went to only one because i thought it was some how overheating. But it does the same thing with one XFX card. I have alternated the cards, and does the same. Im able to view the ASUS PC PROBE while playing Left 4 Dead II in a full window mode. It dosnt appear to be overheating. On idle the CPU - 32, MB - 29, Both north and South Bridge around 50 - is this normal? When under strain the CPU goes to about 50, MB - 38 and north and south bridge stay pretty much the same! I am sooo confused, I just dont understand what could be causing this! Everything in the PC is new except for the XFX Cards, these were second hand, but seem to be fine when playing not so intense games. Any ideas would be greatly appreiciated!