BMW: BMW 1986 535i electrical problem, ford trucks, time jon

Question
I'm trying to fix the power windows on my friend's bmw.  She got it after it had been wrecked.  Apparently the windows used to work but then stopped working...I've only worked on older Ford trucks and was just wondering where to even start.  I looked at it today and was just totally confused...any advice?  Thanks for your time.  

Answer
Jon,
 As you've noticed, there is a little more going on than a typical Ford truck, but it can still be fixed.

 I would first start by checking the fused relay.  Around the radio there is "usually" a button that pops in or out, and it's like a breaker in your house.  Sometimes it gets pushed in/out and disconnects power to the windows.  If the car doesn't have one, I would take a multimeter and check for voltage going to the window switch, that will tell you if you are getting power to the switch.  If power is getting to the switch, then the problem lies between the switch and the motor.  Test the lead coming out of the switch for power.  If you press the button and get 12volts (or more), then the switch is working and the problem is in the wiring or the motor it's self.  It's hard for me to believe that all 4 windows have bad motors in them, so I think it's a wiring issue.
 If you get stuck, dont hesitate to ask for help,
 Josh