BMW Repair: On Board Computer, 7 digits, beemer

Question
I have a 330 ci convertible that I just purchased.  I used the GPS and returned to the radio which now will not turn on. I "terminated guidance" properly but I cannot get my sound system to work.  

Answer
Dear Michael,
Please tell me the year of your beemer. Better still tell me the last 7 digits of your VIN. And does your on-board display have left and right display partitions or is it just one squarish display?
There are many 330 ci's and even models of the same year have different accessories installed.
Tino