In reply to rockwing:
I'm assuming that the footage is not encrypted like retail movie/DVD which means that any movie editing software should do the job for you.
You just need an option that will allow you to copy the audio only. I do not know if the free Windows software does this but I do know that Adobe Premier Elements and Power Director have both these features. The only down side is that premier Elements and Power Director are not free, but there are plenty of free options out there that will do the job for you.
Check out Blender, Lightworks and DaVinci Resolve (I use Resolve)
Post edited at 12:08