Two things come to mind. Check your fuses. Even if they look OK, give them a twist. Make sure they are not corroded. Also, I think there is a control relay for the power windows. I believe it's located aft of the fuses, but I am not sure of the exact location for your car. This may be the problem component. Lastly, wiring, but that can get complicated. Steve or Donnie might have better detail for you. Good luck...
1987 BMW 325