loud screeching/glass broken noise. one side opens and closes with noise. other side opens but won't close, have to manually raise it. Is it regulator or motor?
power windows issue on 2001 BMW 330i
These cars have a little plastic guide that breaks and sometimes causes the window to exhibit these problems.
2 more answers
In these cases, it's almost always a problem with the regulator. Problems with the motors are more uncommon. The labor to replace is very similar, though. If it's a problem with the motor, you will be out the additional part cost.
I just experienced this problem a week ago, it was a pulley that was broken.