In Windows Vista, Microsoft has decided to remove the Hardware Abstraction Layer (HAL) for DirectSound and DirectSound3D. The HAL is the software layer that on previous Windows Operating Systems enabled an audio accelerator such as the SB X-Fi, to provide DirectSound3D applications with hardware accelerated audio. This enabled soundcards to perform tasks such as sample-rate conversion, mixing, 3D spatialization using HRTFs, filtering, and effects processing. Without the HAL, DirectSound on Windows Vista will be rendered in software with no advanced functionality such as EAX.
The audio changes in Windows Vista do not affect OpenAL however. For audio cards that feature 'native' OpenAL support, SB X-Fi series of cards, there is no need to worry! Games that enable support for OpenAL will continue to run just as they do on Windows XP - with hardware accelerated audio and effects.