5.1 to 2.0 (or DVD to CD)

I've searched (and not found) any cheap (free?) software for converting the sound off DVD video to .wav or CD format. This is because I've got some concert DVDs and a couple of other movies (Koyaanisqatsi & Baraka) that I'd like to be able to listen to on the car CD/MP3 player.

Having the hard-drive fritz last month and losing all the lovely OEM stuff that I previously enjoyed is a bit of a problem also...

Any ideas or recommendations (or links to previous threads)?