i have a 1991 Bmw 750il and the battery was disconnected and now the "code" is now taken over my radio. i do not have the manual and the last 7 digits of the VIN are dc79296

Just remove the radio, search for the radio number on the back of it, drive to the BMW dealer and he can tell you by checking the system.
Often it is also written down in the owners manual, check that too.
http://www.bimmerboard.com/forums/posts/462147/

or via the internet
http://www.bimmerboard.com/forums/posts/462146

you may also want to check the audio forum...there was a guy there that had access to the radio CODES database...and all you needed to do was post up your RADIO'S serial number (not the car's VIN).

Anyone that has a BMW anti-theft radio that requires these codes...need to make sure they have them etc. ...if you don't...you need to make haste to get them because rumor is that BMW is dropping this info.

Consider yourself warned. :D

Yeah, there are a couple people in the audio boards that can do this. I have used them a couple time already.