I'm having a hard time getting multichannel sound to come through from my Asrock deluxe3 motherboard.

I was following the instructions from Microsoft Get high-definition sound and music from your computer. The problem is that when I go to "Sound" and try to configure my speakers, I only have the option for "Stereo". I am attempting to send the audio over the video card's HDMI.

I've called evga tech support and they claim that the this is caused by an onboard sound driver issue. I've tried the driver on the cd which came with the motherboard, I've tried searching online. I've tried clearing drivers, reinstalling drivers, and i've even tried completely reformatting my OS from Win 7 64 bit to 32 bit. Nothing allows me to have an option other than Stereo in the sound settings.

Sound does work in two channel only, but I don't get multichannel sound.

Any help would be most appreciated... if not I assume I'll just send the board back and try another brand.

System: (brand new build)

Windows 7 (32 or 64 bit) - have tried both
Asrock P55 Deluxe3 motherboard
Intel Core i5 750 processor
EVGA GeForce GTX 460 1GB