Here's how I enabled my Sound Blaster 2 ZS on my Vista x64, running AMD Opteron:

Caveats:

a. The steps below are what I did. I don't know if you really need the XP 32 bit drivers first. It may be possible to do it with just the Vista beta and XP64 drivers. There may also be better ways. Please do update this thread if you find any!
b. The steps below are for Audigy 2 ZS only, NOT Audigy 2 ZS gamer, platinum (pro), or other models. There are existing drivers/workarounds for these other models.
c. The steps below are for AMD 64-bit processors. They have not been tested on an Intel processor based PC. It may or may not work, but you can use the drivers in the "i386" folder instead of the "AMD64" folder.
d. Do this at your own risk! Be sure to backup your PC!!! Whatever happens, it's your fault, not mine

Needed: Windows Vista Beta 2 Build 5384, WinRAR, Creative Audigy family Vista beta drivers, Creative Audigy family XP drivers, and Creative Audigy family XP64 drivers. All of these are available online for free and perfectly legal.

0. Use CompletePC backup to create a backup of your OS state in case everything is f'ed up!
1. Use WinRAR to unpack all the Creative drivers into separate folders. Rename the folders so you don't get confused which are for Vista, XP and XP64.
2. Goto Vista beta drivers folder/Drivers/Support/amd64/
3. Right click on "ctzapxx.exe" and select "run as administrator"
4. Install the driver, reboot Vista.
5. After reboot, there's no sound and sound icon on taskbar has a "X" on it. That's normal.
6. Repeat steps 2-4 with the Creative XP driver, but choose "overwrite existing shared Creative drivers", then reboot. After installation, you'll get a BSOD. Let Vista reboot on its own.
7. Repeat steps 2-4 with the Creative XP64 driver choose "overwrite existing shared Creative drivers". Reboot, and you should now have sound!

Optional:
8. Use control panel to change the sound quality. At the highest "studio quality" setting I get crackles and pops... Sound is ok at lower setting.

Good luck, and have fun with your ZS enabled Vista! Oh, and please do let me know if you find an easier way

[EDIT 21/06/2006]
1. Corrected a couple of typos.
2. If you're using the 32-bit (a.k.a. x86) version of Vista, use the NGO modded drivers for Audigy, available from the NGO website. I've tested it on the x86 Vista, and it's useable (not perfect).

This post has been edited by shreaker: Jun 21 2006, 12:57 AM