Vista - I can't set 5.1 audio on Vista

First, sorry for my poor english, since I'm a spanish guy.

I cannot set 5.1 audio, no matter what I try. I have an ASUS P5Q mobo with a Realtek sound chip incorporated.

I have the speakers connected through an amplifier using the rear SPDIF Out (Digital RCA) connector.

My system is up to date (including latest Realtek HD r2.10 drivers), and I cannot access the "configure" botton under Vista. It's in grey, and I don't know what I'm doing wrong.

Can anyone please help me?

I assume you are referring to the speaker settings in the Vista controls and not the Realtek one. If so are you clicking on Speakers or SPDIF Out?

Regarding the 5.1, unless your onboard has Dobly Digital Live (DDL) or some other kind of upmixing; unless you are playing a 5.1 source you will probably only get stereo out using the SPDIF (same would apply if using the analogur connection).

Yes, I'm talking about Vista configuration, through SPDIF Out settings.

I'll have to check the DDL thing, since the whole thing is unkown for me.

If I play from a 5.1 source, I have no problem and everything works just fine, DTS as well.