ASUS P5N-SLI nforce 570 SLI Socket 775 Motherboard problem.....?

ok, so i wanted to build my own custom pc. i got a core 2 duo, ATI graphics card, 2 gb ram. and then i tried to over clock it. i think i chose FSB or something like that, now, when it restarted, nothing showed up on the screen.... any ideas?? i tried pressing the restart on, and it didnt work, it did b4. thanks