There is actually a way that you might save it as AVI. If you download MPEG Streamclip, it should come with an extra Quicktime component called Save-as-AVI. Put this in Home/Library/Quicktime and you should have the option to export to an AVI just copying the streams in the MOV.
This might not be 100% reliable, though. I suggest you try playing it back in multiple different players (Quicktime, VLC etc) to check that it works.