I've finally cracked it - my X-FI gave me 5 channels of glorious static the first time I tried creative's awful drivers but now.. it works.
So, in the hope that this is useful to someone else here's how to do it:
Download these modded auzentech drivers - they'll install on your X-FI. This will cure the 4gb issue and should resolve popping too. Uninstall previous drivers first (and reboot).
http://files.filefront.com/Drivers+X...rar/;8661284;/
http://files.filefront.com/SBXF+AudC...rar/;8619338;/
Now, you'll have one more problem - you'll only get sound from some of your speakers in 5.1 (just the fronts) - set them to 7.1. Yes I know it's crazy but just do it.
Now download (if you haven't) the X-FI Vista CD (it contains all of the creative apps - you probably got an XP with your card).
http://files.filefront.com/SBXF+SIVI.../fileinfo.html
Start the installtation but ONLY INSTALL the THX utility. Run this up and you'll be able to remap your speakers - you need to do this because in 7.1 mode your rears will be configured as the side speakers (so they don't work) but remapping them will get the rears working.
Sit back and enjoy
Hope that's some help - it's been driving me nuts for a while. Backing up your system is always wise and i can't be responsible for any damages. This worked very well for me