I did this using Goldwave and recording wave outs while playing the DVD (this is on an Audigy 2) with the Creamware you could just re-route the audio to VDAT or whatever
I've done this using DVD Decrypter and DVD2AVI, both of which are bundled in Gordian Knot. DVD2AVI has a Wave extraction function that'll pull out the whole soundtrack (Audio -> Output Method -> Decode to WAV, then just save the project.)