This issue could be caused by a few things, so its important to describe the different ways to connect your GPU to your DLP.
Using the HDMI connector on the GPU to plug directly into the DLP HDMI input
For this configuration, check to make sure that you have connected the S/PDIF connector from the motherboard to the GPU. Please check with your motherboard manufacturer to ensure it has the correct S/PDIF connector.
If your motherboard does not have a S/PDIF connector and you wish to use the analog output on your motherboard to connect to the DLP, follow the instructions in Using the DVI connector on the GPU to plug directly into the DLP below.
Using the DVI connector on the GPU to plug directly into the DLP using a DVI to HDMI adapter
3D Vision ships with a DVI to HDMI connector that can be used to connect to the HDMI input on the DLP. In order to connect analog audio from your PC to the analog input on the television to use the television's speakers, follow these instructions:
1. Download the 3D Vision DLP Hotfix.
2. Connect your PC's analog audio into the analog input on the back of your DLP. Mode DLPs use left and right RCA audio inputs so you will likely need a cable called "3.5mm Stereo Headphone To RCA Adapter Cable" to connect your PC to the DLP.
3. Run the 3D Vision DLP Hotfix. Make sure you are running this as an Administrator on your PC
4. Follow the onscreen instructions to disable HDMI audio. Note that this DLP Hotfix will also toggle the HDTV Resize Desktop compatibility mode. For more information on that mode, please read this Knowledge Base article.
5. Reboot your PC.
6. If your DLP requires any changes to its settings, use your DLP remote to configure the audio input.
7. Start up your media player and adjust the volume to a comfortable level.