How to fix 5.1 analog surround sound in Media Center 2005 Update Rollup 2

There is a known issue in Update Rollup 2 for Media Center 2005 that causes 5.1 analog surround sound to revert to 2 channel mode. The underlying issue is that a registry setting is being overwritten by Media Center. You can use the following steps to add the registry value needed to fix this issue:

  1. Close Media Center
  2. Click on the Start menu, choose Run and type cmd
  3. Run the command reg add "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Media Center\Service\Video" /v AudioOutputFormat /d {696E1D31-548F-4036-825F-7026C60011BD} /f

Note that if you re-run the Speaker Setup portion of Media Center Setup, this registry value will be reset again and you will need to re-run the above command to fix the underlying issue once more.

This issue was previously described on this NVidia support page, but I wanted to list it here as well in case anyone reading my blog runs into it as well.