Windows Vista, with its migration to DirectX10, will remove the hardware abstraction layer for sound. The impact is that older games which use Direct Sound, and older sound cards will not deliver the same level of sound quality under Vista as they would under XP. Creative, in an attempt to limit the impact on consumers, will be releasing an application called Alchemy which will auto-detect Direct Sound games and bypass the Vista sound system, restoring the lost audio quality.
More at The Inquirer.