Matthew van Eerde wrote:
Are you using this driver for the Creative?
http://tinyurl.com/kca2r

There's this intriguing caveat...

* AC-3/DTS decoding (only in Windows Vista 32-bit)

I am using that driver, but that isn't relevant here. That remark means that the driver isn't capable of doing AC3/DTS decoding in Vista x64. However, I don't need the driver to do it; I need it to output the undecoded signal to my external decoder, which it is perfectly capable of doing (as I said, using the "test" option in control panel and playing DVDs with media center works correctly, just everything else doesn't).