While trying to get the game working I made two observations:
In order to achieve a running base game I had to replace sound.dll.
To launch the add-on I needed to swap sound.dll and audio.dll.
As it is quite unconfortable to move the files manually all the time, I have written a small
app that automizes this process: http://www.imagenetz.de/f18ccdc67/Jpv7Gwz9BuD.rar.html
Just put the files in your game's installation folder and run the app by double-clicking Run_BII.vbs
This game seems to be very sensitive. Several times I found apparently not correctly
ended iprocesses of launcher.exe in the task manager, or experienced crashed
instances of it in the cache blocking a new start of the program. The only way to wipe
out all that debris is a clean system reboot.