The MAGIX Music Maker 12 you have was written before the release of Windows Vista and Windows 7. That program by itself is not compatible with the newer Windows architecture, and its code is no longer supported. This could have a real impact on how things communicate.

I unfortunately do not have that program version any longer. Also, if I did... I doubt I would risk installing it on a operating system that it was never designed to work with.... With that said, is the keyboard you purchased something that works with Windows 7?

Software and hardware changes happen fast, sometimes dramamatically, there is very little we can do with the older titles, but  you might want to try downloading a demo/trial of the latest Music Maker to see if you can get it to function with the keyboard. Since it is a demo/trial you wont be investing any money into it and can see if the keyboard works with software designed and supported for the operating system you have running.