I've upgraded the GPU, and recorded CoD's performance from an outside camera focusing in the screen while fraps shows fps, this was done in that way to not punish performances by recording video.
Original Pc:
I7 920 overclocked to 3,33Ghz
6Gb RAM DDR3
Asus Geforce GTX275
Windows 7 Ultimate 64 bits
Test 1: just before changing the GPU, with the current medium video settings I had.
Test 2: GTX275 replaced by Asus Geforce GTX580, drivers updated, same CoD video settings.
Test 3: raised all CoD settings to maximum and recording at the same time with fraps to try to kill fps.