My guess is that the nav computer is having trouble reading the disk. Try burning a new CD using either ImgBurn (www.imgburn.com) and set the burn speed to 1x.

When you do the update, it does not matter where you are in the Menu (it can be on radio, OBC, nav, etc.), and it does not matter if the monitor is on or off. When I have done my updates, I usually have the monitor on and the GPS Navigation option selected. Make sure the key is set to Position 1, and do not do anything that would disturb the car during the update. Just turn the car on to key Position 1, eject the map disk, insert the OS disk, then wait. The screen will say it could take 6 minutes, but it usually takes less time than that. It does

If you are starting from OS version 3-1/21, you may also need a "Key CD" to do the update. You would definitely need the Key CD if you were starting from either version 3-1/30 or 3-1/31, so you would probably need it for an earlier version. I also recommend that you download and burn a Key CD image too, just in case. You can download it from www.domino.org/old/nav/v18-key.zip or www.e38.org/nav/v18-key.zip

Finally, you can go directly to the latest update CD, no matter where you are starting from. So, using V28 is no problem.

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2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input