My computer turns on then off instantly after I installed I new graphics card and Power supply I need help. I believe everything is plugged in correctly, after taking out the graphics card the PC still won't start the power supply is a 750 Watt smart Thermal take, It should be more then enough to run my system, and the card is a GTX 780. I am new to putting together PC's so it's possible I missed a plug please suggest a possible plug I missed and what the issue could be thanks.