How do I get 5.1 audio to my receiver?

That card should support 5.1 over HDMI. Have you tried movies (pre-encoded digital surround), or is this other content?

your video source must have a digital 5.1 or 7.1 soundtrack. if the source material is just in stereo, then the receiver will usually default to dolby pro logic or something like that.

Understood. I was playing a DVD that is in Dolby Digital 5.1

That's odd. Right click on the audio icon in the tray, go to playback devices, and hit properties on the audio output for the card. In those properties, go to the "supported formats" tab, and make sure that dolby digital and DTS are selected.

Whatever you do, just make sure you don't use Pro Logic of any form.

Use AC3 Filter if you pass audio through a digital connection (optical or coaxial) for movies.

I believe you will not be able to have real surround in games through a connection of that type, however.

I got it to go. It was more of a player issue than anything. I had to install power DVD. I made my adjustments and it works great.