Boschitt, I use my half decent laptop for recording with hyper cam of all things, and it works fine.
First of all, that's HyperCam. I was talking about FRAPS. They are two different programs that work differently.
But, IIRC, Fraps has to record the game frame by frame at your requested frame rate, then compress it down simultaneously then save it to the hard drive.
It is definitely CPU heavy.