I have the same problem ive just upgraded my PC but im still getting 60fps my specs Core 2 duo 2.4, 4 GB memory Dual, dual 8800 GTX, and ive even tried with my old 6800GT all drivers are updated including those for mainboard, sound and so on
Ive tried defrag but no improvement even scanned for virusses, spyware etc still nothing
hmmm