Today I put a new cpu and graphics card in my pc I have 450w psu the new cpu was a Amd Athlon x4 760k 3.8ghz quad core and the graphics card is a Sapphire radeon 7850 OC 1gb.The problem is when I start the pc it tells my I have to press f2 to confirm the change and it gives 15 seconds to press it but it freezes and I cant do anything so it just turns off please help!