Well when you are trying to work with 2 or more audio tracks, doing so in 2
passes as I suggested, then you need to save it to your harddrive (this will
combine the audio and video so the audio that WAS on the audio/music
timeline will now be on the audio timeline) and then import it into Movie
Maker again from your harddrive. As said above when you drag the clip to the
timeline now the audio/music portion will be empty again and the audio
portion will contain all our audio. This will allow you to place another
soundtrack into the audio/music portion once again and adjust the volume
appropriately before saving your movie.
I hope that made sense, I started getting dizzy writing it!
-Wojo