Let me start by posting my PC spec. Core 2 duo 2.17 GHz Overclocked to 3.0Ghz 2 8800 Gts 640 Mb Superclocked Graphic cards In SLI 4 Gigs Corsair XMS Extreme DDRII 800 Ram 2 250 GB Hard drives 1 DVD drive Windows Vista 64 Bit Ultimate Edition. My problem is this. I installed COD 4 and it started up fine. But as soon as I adjusted the graphic settings to High, and the setting to 2 graphic cards and hit apply. My PC turns off. Same problem for Americas Army. Except i get a blue screen, and have to restart PC. I also get the same issue with 3d Mark. As soon as I start the test, It loads then MY PC shuts off. I adjusted my Ram Voltages to 2.o volts, other than that everything is at default. My 680 SLI Mobo has a plugin option on the MOBO itself for SLi Power which I am not utilizing because I dont have the proper adapter. Dont know if that would make a difference or not. So, with all that being said. I am in need of some desperate help here. I have no clue as to what I need to do in order to fix this issue. It seems as if maybe my PC is unstable and needs to be adjusted but honestly I wouldnt know what the settings would need to be as far as voltages, Timing, Etc. I was also told that my SLI ready 680 Watt power supply should be plenty. Anyone out there have any suggestions or ideas as to what I can do to solve this issue. Getting really frustrated here. Thans alot!