BSOD playing Battlefield 3 or rendering in sony vegas

Hello,i recently built a custom PC with AMD FX 8320 3.50 Ghz,MSI 760GM-P23(FX) (MS-7641),Saphire 7770 Ghz edition 1GB,8GB DDR3 1333mhz RAM and 500gb hard drive.The computer works perfectly untill i try to play Battlefield 3,Need For Speed Most wanted 2012 or render a WMV file in Sony Vegas.Sometimes the PC will just restart without any error but most of the times it will just get BSOD.The BSOD...