Pc not working

[Slaysher1223]

Ok well I have a gigabyte motherboard I recently bought a new crossfire 850w power supply and a GeForce gtx 680 classified graphics card. Idk if I messed up somehow but I put the new power supply in and the graphics card right after. But the wierd thing is when I have my 24 pin in all my leds and fans go on but when I put the 4 pin in it just doesn't work any help please?

 

[greeneman42]

When you connect the motherboard power and the cpu power, the computer doesn't respond to the power button? Are you sure you're plugging everything in?