Welcome to DH
This forum is for the kX Audio driver, you would be better off asking your question in the following forum (or a Diamond support forum):
Audio General and Technical Discussion
Aside from the above, DirectSound3D was removed from Vista, and that is likely what is causing your problem (with games that use DirectSound3D). I would check with Diamond and see if they have any solutions for you, and/or check the web sites for your games to see if they have any updates for Vista (i.e. maybe adding OpenAL support, etc).