Sigma-Tel is unable to provide you with the needed drivers because of licensing restrictions with Dell and others, and Dell is currently not providing drivers for Vista beta testers. Thus, if the XP drivers don't work you're out of luck until Dell decides to support Vista.
Ok I was totally loving Vista Ultimate until i plugged my headphones into my Dell Inspiron 6000 and no sound came out. So I did a search for my sound driver? card? and this I found a forum and this guy had the same problem I had and somebody answered him by saying go to dell's website and install the latest sound driver. So that is what I did but it still didn't work. I think my sound driver? card? is a Sigma-Tel C-Audio. Anybody have any suggestion or solutions.