Yes sir. I'm using my HD4850 (DVI-HDMI adapter). Dolby and DTS are okay, except this AAC 5.1. How can I set it up? Is it in the Sound settings then Right Click on the AMD High def and choose Configure Speakers? Then set it to 5.1 Surround?
yes, you need to configure Playback Devices and set the speakers to 5.1
this is what works for me on a laptop with intel hd graphics connected to onkyo receivers:
1. right-click the Volume icon on the System Tray, select Playback Devices
2. you'll see a list of devices, one of those would refer to the a/v receiver connected via HDMI
3. select that device and click Configure. this would let you the type of speaker setup that you currently have.
take note that 5.1 may have two options: 5.1 Surround L/R or 5.1 Surround Back L/R; just try out which one would work for you.
also, when you set it up this way 2.0 PCM audio would also be sent as a 5.1 PCM stream (center + surrounds + LFE channel won't carry any signal) which might prevent you from applying processing such as Dolby ProLogic; subwoofer would still work via bass management in the receiver.
HTH
EDIT: added screenshots