I think you need to put the disc in and turn off the ignition wait and then turn the ignition on and it should reboot the nav computer and the new disc should be recognized, I'm not 100% sure, as I don't have i-drive, maybe one of the i-drive guys can confirm the update procedure, what does it say in the nav manual?

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.