I have the (perhaps) the same problem as stated in this other HDMI sound to HTPC question. I tried the advice of clicking on the speaker in the system tray. I can see the HDMI audio device I want to use. That device claims to be functioning properly. But there is no sound, and it won't let me select it as the active audio device.
When I click on the troubleshooter, it says that there are no speakers connected.
I would think this is because my computer us unable to pipe sound through the video card (preventing the HDMI from carrying it), except that it truly claims that it has an HDMI sound device that is working correctly. So I'm not sure what is wrong at this point. Thoughts?
My system is Windows 7 x64. In case it makes a difference, the video card I'm using is this GeForce GTX 560