DVD Decrypter can directly demux a DVD. Now all you have to do is get yourself a copy of DVD Decrypter.

DVD-lab Pro also can demux DVD directly. But this is how I would do it:
• Rip the DVD to your hard, using DVD Shrink (rip to folder not ISO; Select no compression)
• Start up DVD-lab Pro and browse to the folder where the ripped contents are select the audio files.
• Wait a while, while DVD-lab pro demuxs them all, then you have a mp4a or something like it - anyhow you can just play file in WMP and it's just the audio.