Problem with Passenger side rear power window

[kyriele]

Hi All:

Hope someone can help me understand what's wrong (and about what it's going to cost to fix it!) with my rear passenger power window. From the master controls by the driver's seat, the other 3 windows open and close. The one window in the back was up on Saturday and while driving dropped a couple of inches. Then dropped a bit more. It's now halfway down and pushing it up by hand doesn't help at all. Odd thing is, sometimes when I play with the switch it will make the whirring noise as if it's trying to do something...other times? Nothing.
Any ideas? Any thoughts or suggestions are gratefully appreciated.