The best thing to do is get the 14 digit serial number off the radio and take it to your nearest BMW dealer and they should be able to give you the code.
You can also try Instant-Radio-Code.co.uk (there is a charge for this service)
Donut
March 2008
I can answer this question...
How do I retrieve my lost radio code ? Bmw 540i e-34 1994 model?