A quick heads up for X-Fi owners; Creative has just released an updated driver (version 2.18.0008) which supports all X-Fi series cards based on the CA-20K series of audio processors. If you're not sure if your card uses one of those, it's used in the X-Fi Titanium Series, Xtreme Gamer Series, Xtreme Music, Platinum and Elite Pro.
The new driver brings back full Dolby Digital and DTS decoding for certain models in Windows Vista environments and DVD-Audio playback is now possible for cards under Vista 32-bit that came with the MediaSource DVD-Audio Player application.
What's probably going to be most useful for some of you is the claimed fixes for issues involving audio popping/crackling during AC3, PCM or DD playback via the digital output(s). Further to that is a fix for CMSS-3D woes when in the Audio Creation mode.
You can find the new 2.18.0008 driver available for download at Creative's Worldwide Support website.