That is weird. I've always used x-fi cards and never once did I have this issue.
But at this point try uninstalling all creative software installed -if any- and from the device manager right click on the device (should be with a yellow ?) and uninstall it while also checking the box to delete all drivers for it just to be sure.
Shut down the pc and remove it from the system. On reboot enter the bios and make sure on board sound is disabled. Let windows load as usual. Shut down again and insert the x-fi once again, preferably in another pci slot if available. Let windows load again and proceed to installing the drivers in administrator mode. Right click on the creative drivers and select Run as Administrator regardless.
I hope that will do it as I would not know what else to suggest