If you remove the regulator and motor, you can test them individually - the motor should spin forwards and backwards smoothly when reconnected to the switch. It can be operated after unbolting it from the regulator.

The regulator mechanism (pulley and sliders, etc) should slide by hand once the motor is removed (the gearing creates a lot of drag). It is no fun to tear it all apart just to troubleshoot, but that's the way to find out.

__________________
David.X5
2001 X5 4.4i Sport
SOLD! at 160k miles