at a push, just spark up the wave editor of your choice, and set your soundcard's record input to "what you hear" and then do it by hand.
there is a package to do it, but I am buggered if i can find it or even remember it's name...I think it's actually something really cryptic like "dvd audio ripper".
Some dvd ripping software will allow you to set audio only output formats, i assume tat would also do the trick.
if you're only gonna do this once, grab a warezed version of something off demonoid or somewhere like that....it'll be less painful than windows freeware, and you'll be able to read if it works or not efore getting it! If you plan on doing lots of it, play nice and buy it.
Course the easy answer is linux, libdvdread, transcode and Lame.....but it's a bit of a length to go to :D