There is a free version of fraps but every 10 (I think) minutes of recording, the recording stops, so you have to hit record again. There is no way to get the full version for free.
Fraps does record sound, however the videos it makes are huge, like 3-4GB for every 5 minutes or so of film. You can sort this pretty easily by putting all of the parts (it creates a new part every few minutes) in Windows Movie Maker and publishing it, which will make it the size it should be of 1GB for every ~hour of recording.
An alternative is to use Xfire, but I always found Fraps much better