Replace the window switches. Most likely busted up inside. The power to the windows goes through the switches first.
If you think the switches are ok then you have to power the window motors directly to see if they are dragging. Best to remove the door panels to check. I've found the connections at the motors to be a bit corroded. Also you can clean and relube the window gears.
If you don't want to pull the door panels you can still run the motors from the connectors on the backs of the switches.
This is the schematic for the early window switches:
http://www.pelicanparts.com/944/electrical/944_84_elec_windows.jpg