There are three reasons why you may not hear audio:
1. Your speakers may not be connected and/or your volume is too low. Make sure the proper cables are connected and the volume is set to a level that you can hear. Also, please check to ensure that your volume control is not set to "Mute."
2. S/PDIF mode is enabled but the cable to your external receiver is either disconnected or the receiver is not on. Check to ensure that the proper cables are connected or turn off S/PDIF mode.
3. You are trying to watch a DVD-Video using an application that is not supported. The NVIDIA PureVideo Decoder contains a video decoder and an audio decoder that are compatible with many third party applications. The video decoder is compatible with any third party application that uses Microsoft DirectShow interfaces for accessing decoders. The audio decoder is only compatible with Windows Media Player 9 or higher and Windows Media Center for DVD playback. However, you can still configure the NVIDIA PureVideo Decoder to use S/PDIF mode with any third-party application and output audio to an external decoder.