I had the same issue, the HDMI device didn't show. I did manage to get it to work (how -> see below) and then I could set it to default. This did NOT solve the issue for me (although it does seem to work for many if you read the forums).
Try this:
- open Control Panel => Device Manager
- Click the little triangle on the left next to "sound, video and game controllers" to make it drop down
- You'll now see your sound devices, I for example have 2, one is "ATI..." the other "Realtek..." (depends on hardware obviously)
- Right click each one in turn and click "disable". Click "yes" when the warning pops up.
- When they're both turned off, right click each of them again and click "enable".
Should work fine now. If you click the sound icon on the bottom right of your taskbar it should show an icon of your TV (actually HDMI) now rather than the standard speaker symbol.
Kind of annoying for me, I need to do this every time I hook my laptop up to my tv... but it works. No idea why though, but it does it for me.
GL