So I have a Hantol HPSU585P 585W power supply and a AMD Radeon HD 6950 2GB GDDR5 graphic. When I first got my graphic, it worked perfectly with this power supply on Win 7 64bit, then I decided to format my PC and after that my computer won't turn on unless I remove my graphic. I first thought that the graphic was the problem until I decide to try it with another more powerful power supply (850W), and then it worked great. I mean if the graphic didn't get enough power, how did it work before?? I really don't understand how can this happen? Can anyone help me please..?!