There are two differant types of BMW nav DVD's, the Professional and High edition. You could have the wrong one with your drive. Now you can check the current version of firmware and update the firmware if needed.
1. You can learn a lot more about the MK4 navigation system here:
http://www.xoutpost.com/electronics/navigation-system/ it is very interesting to see all of the changes the guys at the BMW forum have done, like night mode, and voice activated points of interest.
2 and next you will want to download NavCoder here:
http://www.siegenthaler.co.nz/NavCoder/
3. and then navTweek to write your own custom firmware:
http://www.xoutpost.com/electronics/nav ... tweak.html
4. then
http://www.pimp-my-nav.com/ to custom modify the Points of Interest on you DVD nav data disks, like adding red light cameras and speed cameras
5. then you will also want to order the Resler iBus interface
http://www.reslers.de/IBUS/index.html so you can connect your laptop to your Range Rover and modify the language (I added Russian for fun) and change settings in to Light Control Module to accept LED bulbs, etc
You will really begin to appreciate the work the guys at BMW did to improve the Range Rover.
WARNING: If you have an MK3 Range Rover CD based navigation and perform any of these upgrades or modifications your unit
WILL NOT WORK ANYMORE!