if all the other windows are working,then it could just be the switch for that side,try swapping over the passenger side switch to see,check also that the wires on the switch are connected up properly.
Is there any movement at all? Does the motor run but the window not move? if the latter then the window may have come off the track. If the motor does not work then it's either knackered or the connection to it is faulty as norman says, check the switch, connections etc.
the motor dont move, the back window on that side doesn't work either so i doubt the glass as come off the track. probably what norman says i'll check it out. thanks