Creative has received much criticism for charging owners of Audigy sound cards for its ALchemy software, which offers improved audio support for certain games under Windows Vista. However, a modder by the name of Daniel Kawakami has managed to build hybrid drivers using a combination of XP and Vista files as well bypassing certain driver checks to enable several features including:

• Dolby/DTS decoding
• CMSS, CMSS2 and Stereo Surround (originally only CMSS was available, but this setting also affects ALchemy/OpenAL and Kawakami notes that it's thus particularly useful)
• Advanced EQ and Special FX presets
• DVD Audio
• Hardware MIDI synthesizer (Kawakami says he wrote a small utility that automatically detects and changes the default Vista MIDI Synth during driver install or can change it later using its GUI. Some media players let you choose the MIDI synthesizer)
• Equalizer
• WaveRT

You can read some more complete details of his work at Custom PC and download the files from here. The modded driver was originally uploaded to Creative's forums, although the company responded in a somewhat heavy handed manner, as you can see in this thread.