HD4850 to Onkyo 607 HDMI Audio Problem



I just setup my HTPC and am trying to connect it to my HT and unable to get sound.

I have spent more than 1.5 days trying to get it worth doing Google, AVS searches with similar problems and trying fixes, but haven't gotten it to work.

HTPC Specs:
- Processor: Intel Core 2 Duo E5400
- Motherboard: Gigabyte GA-EP43-UD3L
- RAM: Corsair 4 GB (2 GB x 2) PC9600 DDR21066
- Graphics Card: Gigabyte ATI 4850
- Sound Card: Turtle Beach 7.1
- Optical Drive: Samsung DVD+/-RW
- Hard Drive: 2 x 1 TB Hitachi 0A38016 7200 RPM SATA
- Card Reader: Rosewill 60-in-1 Card Reader
- Power Supply: Antec NeoPower 550w SLI (already have)
- Case: Cooler Master CM-690 (already have)
- Operating System: Windows XP SP3

I have the 4850 hooked up to the Onkyo 607 via HDMI using Input #1 and using Port. I installed all the ATI drivers and the ATI HDMI Audio driver and still don't get sound. I tried going to Volume Control -> Options -> Mixer Device in XP and choosing ATI HD Audio, but I don't get that option. Instead, the only option I get is the Turtle Beach Sound card.

How do I go about fixing this?