I'm guessing you aren't you in North America? The Candian market, as far as I know, doesn't have '07 745's anymore. But that wasn't your question...
You might be able to find the same system in a 745. If the "computer" of the iDrive is different in each series, then the iDrive computer might be swapable/upgradable. At least in the E38's navigation system it is. Not too familiar with the E65's though.
As far as I've heard, however, the iDrive for any series is the same on every model year...but again, I'm not sure.
I did a search for it over on the E65/66 Roadfly Forums and this is my search results:
http://bimmer.roadfly.com/bmw/forums...ural&o=default
The E65 Roadfly Forums seem pretty active, you might try posting there for your answer, registration is free.
http://bimmer.roadfly.com/bmw/forums/e65/