Amazing how a bit of sunshine and a pint of beer puts you into a good mood..

A quick overview of how I might attempt the original requirement, mp4 video and redo the audio track.

There are other ways and other applications. Normally I use linux for this sort of work but I wanted to see how M$ fares, so this is in a Win7 32 bit virtual machine. Uses Avidemux and Audacity.

having a tidy up - everyone finished with this ...going..going..gone
http://www.youtube.com/watch?v=zVhYnKDTXGM&hd=1 7 minutes

There is a Linux distribution called AVLinux. It is loaded with all kinds of AV programs, so you could test them and see what works best for you. It comes as a live ISO file,so it could be run from a DVD, thumbdrive, or in VirtualBox.

Note quite as easy to use, but ffmpeg/avconv and mencoder does the job for me. For wave editing I use GoldWave, which has been my RockOnRockOn! wave editor since Windows 3.11!!