GA-Z77X-D3H Surround 5.1 not working, help?

[callmethebreeze1]

Hello All-

I have this motherboard:

http://www.gigabyte.com/products/product-page.aspx?pid=4144#ov

And am currently using the onboard audio. I have optical out going to a 5.1 receiver, but only my front, left and right speakers are being used (not the rear left and right, as in a functioning 5.1 setup).  I have messed around in the VIA HD audio dock, and cannot find any settings anywhere to enable 5.1.

Can anyone advise?

Surround works fine with my xbox, so the receiver is not at fault.

When I right click audio devices in Win 7, select the optical output option, Supported Formats tab, and run a test on Dolby digital, it works correctly-- all speakers get used.

But for the life of me I cannot get anything else to use those rear two speakers-- I've downloaded a 5.1 surround audio file that didn't work on either.

Anyone have any ideas for how to configure this onboard sound card?

Many thanks.

[Old School]

More than likely you haven't set your options correctly in whatever application you're using to play digital 5.1 audio. In Media Player Classic Home Theater, for example, one has to go into the options, click on the Internal Filters heading, double click on the AC3 transform filter, and enable S/PDIF Passthrough there.