When I installed Vista last week I ended up with an installation that had no sound. I researched the sound issue and found that Creative did not have Vista drivers ready and that their beta drivers were very suspect.
I was resigned to having no sound until March when the production drivers were scheduled to be released.
This evening I was messing around with the options and properties of the existing driver and accidentally ended up with sound! Unfortunately, I was not performing any type of scientific method so I have no idea what I did in what order to achieve sound.
I also did not completely resolve the issue. While I do have sound, I only have two channel stereo sound. This coming from a 5.1 surround sound setup. But any sound is better than no sound at all.