Please perform the following steps to troubleshoot this issue:
1. Ensure your computer system meets the NVIDIA Purevideo Decoder system requirements for Audio.
2. If your computer system meets the requirements, please make sure your computer is running the latest drivers for your Audio Card that are compatible with Microsoft Direct Sound. Please visit your Audio Card Manufactures web site for driver updates
3. NVIDIA minimally requires using Windows Media Player 9 but we highly recommend using Windows Media Player 10 for the PureVideo Decoder.
4. Please update to Windows XP service pack 2 and Direct X 9.0c for the latest Microsoft Operating System and Direct X runtime fixes.
5. Use the Microsoft Decoder checkup utility to ensure the Decoder is installed and has priority if other 3rd party decoders are installed.
If the above utility does not work, please uninstall all Competing DVD Players / Decoders such as WinDVD, PowerDVD, Interactual, and 3rd party Audio Decoders such as AC-3 filter.
Thereafter, please attempt to playback DVD video within Media Player 10 or Windows Media Center.