Just did a fresh install of Win 7 x64 Home Premium on the Zotac H55-ITX.
I downloaded the drivers from the Zotac website and installed the latest Realtek drivers rtl_hda_vista3264.The drivers do not work.
I get no audio from the back panel LR Channels at all. I set it to stereo - no audio. Set it to 5.1 or 7.1 and it is the LR RR Channels that is play through the LR Channels
The front panel audio works and detects when you plug in the headphones.
The motherboard is not faulty. I ran Ubuntu 9.10 on the system and it played perfectly through the front speakers.
And yes, I uninstalled the drivers and reinstalled them again.
Discovered that under Control Panel > Hardware and Sound > Sound > Speakers there is no LR - Rear panel listed??
The three listed are LR front panel, LR RR Rear Panel and C Sub Rear Panel.
As of 9 Aug 2010. There still is no solution.