Did you try any of the suggested things?
And When I said post a dxdiag report, I meant the text file - did you even read the whole sticky?? I mean, I even put a link in my sig to make it easier for noobs to notice it....
*Sigh*
Well, I've seen this kind of thing happen before. Try lowering your resolution and make sure that nothing is forced on in your NVIDIA Control Panel (like AA or AF)

Oh and guys, I really doubt that he even knows what overclocking is.