OK, As usual I wish you good luck and hope everything will work out for you.
Anyway once you are done use the link I gave you here [ http://www.xtremesystems.org/forums/...ad.php?t=81429
] and install the newest drivers for your cpu, it can sometimes help a great deal to performance.
Either way, please report to me of how well did reinstalling work for you.
Also before you go do it, read this: http://techist.com/showthread.php?s=&threadid=61766
the first two possiblitys he brings up are not completley impossible to be your problem.. though unlikley they are.