How do I get the audio to work on Windows Movie Maker?

I am making a video spoof of "Time Traveler's Wife" for an english project on Windows Movie Maker. We used two different cameras to film the movie, the ones used from my pocket camera work fine, and the audio is there. We converted the ones from my friend's video camera from an .mod form to .avi, so they play in the movie maker, but the sound doesn't work. What do you do?