Digital surround sound (5.1) stuck on stereo - Soundmax driver

Hi,
i need help getting the sound to work properly on vista. i know the sound
card works properly because i have a dual-boot system and the audio works
perfectly in XP. So the problem lies in Vista....

OS: Vista Home Premium edition
Motherboard: Asus P5N32-E SLI
sound card on motherboard: Supreme FX
Driver from ASUS website: v6.10.2.6110

Result: when i right-click on the volume icon in the sys-tray and choose
Playback Devices from the contextual menu I am enountered with different
outputs to use. The surround sound speakers for my computer are not analog,
they only work with digital inputs, so i click on the speaker entitled
"Digital Output Device (SPDIF)". and i click Set Default button. once all
that is done, any sound that comes out of my speakers is stereo, regardless
of what application is making the sound. movies or video games all play in
stereo.

I CANNOT CLICK ON CONFIGURE TO CHOOSE THE SETUP FOR THE DIGITAL DEVICE. the
only thing i can do is click on properties and choose what type of inputs the
device can understand; when i get to the Advanced tab (while checking the
properties of the digital device) all of the default formats in the dropdown
menu are all in stereo.

this is really bugging me and i would really appreciate help. if there is a
soundmax driver that will let me have the soundmax panel (like in vista) that
would be even better, but i cannot find a driver that will allow me to do so.
i've tried installing a lot of drivers from asus (there may be one that works
that i haven't tried) and nothing is working.

Andrew.