Well, I knew that Vista supported using XP sound drivers. So, I found the last know drivers for XP -- the 5.12.2568.0 beta drivers -- and tried the installation. Vista choked on some missing sections and incorrect information in the driver INF files, so I modified the INFs a bit to suit the OS.
The result is here:
Aureal Vortex2 8830 users, rejoice! You now have basic sound support in 32-bit Vista. (If you have a 64-bit system, I'm sorry -- there never were 64-bit drivers for this card, and I can't help you get them).
UPDATE (7/27/2009): More stable drivers have been posted; please see my other post.
UPDATE (6/12/2009): MegaUpload is officially on my shit list for getting my original file confused with what appears to be some game. The download went from being about 18 MB to 459 MB. I've removed the MegaUpload mirror link.
UPDATE: I've been seeing some strange issues that appear to be related to this driver. Specifically, the Windows paged pool on my system seems to be growing slowly over the course of several days from about 150 MB up to 1.5 GB, causing Windows to eventually stop responding. The Windows driver verifier reported that this driver is attempting to free memory it has already released, which is causing problems for the kernel memory allocator.
This may be because these drivers were BETA drivers for Windows XP made by some of the developers from Aureal, and I would like to switch over to using the earlier official version of the drivers that Microsoft bundled with XP as it should be more reliable. Stay tuned.
UPDATE (3/29/2016): This old article is still getting a lot of attention, apparently. The 2shared link has somehow turned into virus clickbait, and I've gotten many, many requests over the past few months to repost. So I've move the link over to Dropbox instead. I've also added a note that these drivers are 32-bit only.