avidemux works fine for me under w7 ... maybe try reinstalling it?
in any case, just google for "convert mov" ... it brings up tons of stuff, can't recommend anything though because I never use movs.
I can advise you not to use avi container, it's used a lot but actually pretty outdated. I personally use mp4, but mkv is supposed to be pretty good as well. h264 is the codec of your choice in any case.