BMW Questions? Ask a BMW Repair Expert for Answers.
try this procedure:
Insert the keys and turn on the ignition. It does not matter whether you start the car or not.
Put the window all the way up (if you are able).
Press and hold the window switch in the up position for 10 or more seconds. Do this with the door closed.
Open the door to make sure the window drops as it should. Close the door to make sure it goes back up again.