If you can still hear the motor running, it is the regulator, not the motor. On an E36 a dropped window nearly always is: the plastic guide clips that hold the glass to the cable mechanism are the known failure point, and when they snap the glass falls into the door or hangs at an angle while the motor still whirs.
The quick split:
- Motor runs but the glass does not move, or moves crookedly: the regulator.
- Nothing happens at all and the motor is silent: check the switch, the wiring and the motor first.
Getting in. I remove the door panel (screws behind the trim caps, plus the handle and armrest fasteners), lift the panel up and off its top rail, and unclip the vapour barrier carefully so it can reseal. The regulator unbolts from the door and comes out through the access holes. The motor usually transfers to the new regulator, but complete regulator-plus-motor assemblies are cheap and save the fiddle of separating them.
After fitting, reinitialise the one-touch and anti-trap function. With the door shut, raise the glass fully and hold the switch up for a few seconds past the top, then hold it down past the bottom. That teaches the module the new end stops.