It depends on what resolution you're operating at.
I'm now running an AMD 4200+ on a 939 platform overclocked to 2.7G with 2G of ram operting with XP.
I also have a HD 4850 with the core running at 660 and the memory running at 1060.
On the crysis GPU benchmark, I get 34 fps with the resolution set at 1920 x 1080 with all setting on medium except for the shaders, which is set to high.
For more info check this sight ought, http://www.gamespot.com/features/6182806/p-6.html