What OS are you running ? Vista has 32 and 64 bit ! I have the X-fi 7.1 but i use 5.1. Firstly, I have a duel boot system. My first is xp32 bit and the X-Fi is superb ! Downstream mix also ! However my second drive used to have Vista ultimate 64bit, which well as any Vista user knows, it's not all that good (being polite) and the X-Fi did not work to it's full potential, no creative console or downstream mix. ( dolby suround was still great)
Dumped the Vista 64 and replaced with Windows 7 Ultimate (with mce) at also 64 bit.
Still X-Fi does not have the same potential of use as with xp32bit. It's just a Windoze problem and until the Mfr's like Creative pull their fingers out of their rearends and give existing users some new drivers, then there's nowt you can do.