hello. check out this site: http://www.videolan.net/vlc/. download the free open-source media player which will allow you to play any type of media including dvd. it also has a built in dts and ac-3 decoder for playing 5.1 dvds on a 5.1 soundcard such as soundblaster live 5.1. hope that will help. i also use windvd 5.1. it's alot better than powerdvd and sonic cineplayer. but, if you are broke, like me, then vlc media player will do the trick. also, check out this site: http://www.sr.se/multikanal/english/e_index.stm. there, you can download 5.1 multi-channel audio files for free. the vlc media player can play back these dts or ac-3 audio files. they're bad ass!
the vlc media player plays dvd audio. and windvd, too. it's just that the vlc media player is free, and windvd costs money.
The newer line of audigy2 cards (the audigy2 zs) and newer cards come with a creative player that plays back dvd-audio (not just the older dvd-video layer of dvd-audio) and supposedly has better support of 24bit/96khz sampling rates although with creative this could just be a marketing claim. Bottom line is it will play back dvd-audio and it sounds pretty good too.