When you applied power to the motor can you feel the motor trying to do anything? Tell us what car this is. On my 83 I found one of the bearings frozen on the motor shaft in the front passanger side and after taking it apart and cleaning and lubing it works fine. Also the brushes could be sticking.
On this post I have some pictures of my window motor when it was all apart.
http://www.peachparts.com/shopforum/showthread.php?t=175953