Does anyone know what it is that stops the window when you roll it down? My drivers side window doesn't stop and falls down in the door and won't come back up.

 

Your window regulator most likely has a broken plastic bushing. You will have to take the door panel off and look inside to figure out the problem.

 

+1 there is a plastic part that stops the window from going too far. The part breaks and you know the rest. The good news is that people have been known to repair the piece instead of buying a new part. Take it out and take some pics. Get this first though so you don't break all your interior panel clips ($$$):

http://www.harborfreight.com/automot...set-66188.html
http://www.harborfreight.com/automot...set-67021.html