Just to be nice, I found one of the workarounds that worked for me way back when.
"With the following settings i managed to activate sound under Vista x64, a onboard "Realtek High Definition Audio" and DirectX10. I think this should work for other onboard soundchips too, maybe someone could confirm that.
1. Click on vista logo (start menu) and then onto system control
2. Open the settings called "sound"
3. Chose from the tabs the "record settings"
4. In this tab you should see something called "stereo mix" if u dont see this right click into the window and check the two settings which appear (something like show deactivated devices).
5. Now you should see the stereo mix, right click on it and chose activate.
When you start Bioshock you will notice the buttons make nice bling bling sounds which means the workaround was successful."