When I'm playing CoD4, MW2, MW3, BF3, or SC2, I normally easily get the Vsync (120hz) with my two HD6950s, and FX-8150... I have 8 gigs RAM, but when I record with Fraps, my FPS drops to 30/40 even in CoD4... The limit is at 120 FPS, so it's not that....
More aboutfrapsing massive drops
Check fraps settings in movies tab. You should be able to select fps at lower left corner.
With the newer games now you can set up the recording and the fps in game and you don't have to have a seperate application to do this.