Movies With More Than One Video Track

Some projects I did back when involved editing some movies in the QuickTime Player 7 which produced some movies with multiple video and audio tracks. These movies were self-contained but retained a multitrack structure. QuickTime 7 has no issue playing these but QuickTime X will not even try. What tool is best to merge (mix) these video and audio tracks into a single video/audio track for compatibility with QuickTime X? Below is a screenshot of the Movie Properties.