here are some things that you can try. first, check windows update to see if you have the latest driver (because there have been a couple posted there.) also, are you setting the multi-channel under sounds and audio devices in control panel? lastly, there was a beta driver just released that is under setember 21 on this site
http://www.fdrsoft.fr.fm/ not sure about the last one though. give it a try. (btw, the official winxp drivers will be released mid-late october. good luck!