If you're willing to save it as two MOV files, quicktime pro is just what you want.
If you want to keep it as an AVI, I think Stuffit Deluxe can archive things to multiple files.
A real long shot is Media Cleaner. You might be able to cut up the movie in QTPro, then pass it through cleaner to create a new, shorter AVI. But for me Cleaner always screws up the mp3 audio, because AVI's aren't supposed to have mp3 audio. A shorter shot would be MediaPipe, but until the next version, at least, MP doesn't support more than one media type at once, so you can have your video and audio, but I don't know of a way to mux them as an AVI