D945GNT & Windows 7 Ultimate (x86) Driver

Hello to all!
I'm experience the following problem.
I have D945GNT mobo, with the Intel High Definition Audio (STAC9220/9223), and I'm use to connect my machine to a Yamaha receiver trough SPDIF (optical), and get Dolby Digital or DTS (It's works perfectly under Windows XP(x86), playing music and viewing MKT movies under Dolby or DTS).
But when I installed Windows 7 Ultimate (x86), and try to configure the audio, everything works wrong. I've download the latest drivers from Intel's web page, or use Vista drivers in compatibility mode, I've only get a very low quality sound (from the rears speakers, It's sound crappy!).
I don't know if anyone has experience the same problem, and if it is, please give a hand, I would aprecciate very much.
Thanks in advance.
Leandro.

Thank u very much for your quick response FZ21Z!!
Yes, I know that is discontinued, but as I've been looking into the internet, there's a lot of pleople compiling his own drivers and maybe here somebody knows something about this mobo.
I've download this codec pack, and also the support for MKV codec, but still sounds like crap.
I've been reading that the main problem is that with windows 7, the signal is not going out to the reciever as is expected to do.
For example, when I try to configure the output for the sound, I use SPDIF, that is ok, in the same screen I've tried to set the speakers out to 5.1, but it reset automatically to 2.1.
I've also one question, If i mount a virtual PC (only for test), It is going to work with the sound that I'll try?
Thanks in advance.
Leandro.