To elaborate on this, Microsoft basically killed DirectSound3D in favor of a software-only audio stack (and the XAudio2 + X3DAudio API they're offering now is far inferior if you ask me, just because of the simple fact that it describes sound in speaker positions instead of 3D coordinates).
However, there's still the OpenAL API, which is out of Microsoft's control and can still be implemented in Vista onward. This is why there are wrappers like ALchemy to restore hardware-accelerated audio in older games.
Oddly enough, Windows 8 is bringing back hardware-accelerated audio, but the damage is done as far as I'm concerned. PC game developers will continue to treat their audio engines as an afterthought and only cater to 7.1 loudspeaker users, which isn't helped by the fact that gamers outside of a forum like this simply don't care.