By the way, how do I know when the regulators are bad? When my drivers side window came off the track a few weeks ago I had my mechanic take a look at it. He claims I need a new motor and regulator. I'm skeptical about the motor, I suspect some lube in the tracks will take care of the poor slidability...
This is exactly what happened to me, which is why I have a spare working regulator/motor in my garage.