What issues are you having with the sound i.e. is it lagging behind the video,does it echo etc?
How have you set windows up to replay audio i.e. defaults or have you used the audio set up options to change the way its played back i.e. hall,chamber etc?
What speakers are you using i.e. one each side of the monitor [2.1] surround sound etc?
Try CCCP codecs and see if rendition is any clearer.
VLC player is quite good for DVD too.