I just found your posts from October, but I am not sure of all the details...

1. You have navigation, correct?
2. Did you do a navigation retrofit? If so, did you use a retrofit harness or a original nav harness?
3. When you say that you "replaced it [the radio] with the correct one," what exactly did you have and did you install? Did you put in a bord monitor radio, and is it an old-gen or a new gen radio? What part number?
4. When you say the radio does not work, exactly what is not working? Does the radio appear on the screen, but you get no audio? Or, is there no radio function that visibly appears on the screen?

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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