OS config HDMI Sound Issues

This is driving me crazy - - Had the mobo in my laptop (ASUS Zenbook) changed as the HDMI port was defective, plug something in, nothing happens to be recognised!. Sent it away to ASUS (well the UK repair facility) they swapped the Main board, got it back HDMI now recognises a connection (to my TV) but no sound! all hardware seems aok now...

Went to the control Panel, under Sound, there are the speakers mentioned, but no "INtel Display Audio". I have checked the two boxes to show disconnected items and to show disabled.
Tried all upgraded sound related updates from INtel (being the internal chip provider).. reloaded these so many times but there seems to be no way of installing things so that it displays the sound item, hence I cannot set this as default so the sound is routed via the laptop internal speakers.

Any ideas how I can get this configured correctly, the item does show up as enabled in the device Manager under Sound, video and game controllers and says its working and all aok??

I have contacted ASUS they are useless and just want me to send it back again and just reset to factory default!

Any help would be greatly appreciated...

OS is win7 64 bit SP1 and updated.