neither do I, but I can record 720p Crysis 2 and 900p League of Legends just fine at max settings..
Just make sure to RUN the game at the resolution you are gonna be recording at.. Otherwise, its just a waste of framerate
It actually depends on which drive you store it to.. I use my external HDD to store the fraps files.. If u have another internal HDD to store, itll give a nice boost to fps