I'm currently using 32 bit Vista Home Premium and an Audigy 2 ZS Platinum sound card. The OS is not recognizing my rear speakers at all. I've tried letting Vista install the drivers itself and I've also used beta and current release drivers from Creative's site.
5.1 sound is enabled in the sound properties tab in Vista along with Creative Audio Console. I've toyed around with different settings and these are the results. If audio console is set to 2.1 and Vista 5.1, all channels play correctly but rear channels play through Front Left and right speakers. If both are set to 5.1, sound is distorted, center and sub don't play, and there is no sound from rear.
Sound plays through rear speakers if I use Dolby Pro Logic II settings on my speakers (Logitech Z-5500). That said, the OS still does not play through the rear channels. This only works on movies and music, but not games or other software.
At one point in the past, my rear-right channel would work. I don't know what I did, but no nothing works.