Unplug the GE Profile microwave power cord from the outlet. Open the microwave door and remove the glass plate and the ring with wheels in the center of the microwave.
Find the metal wave guide shield either on the right side of the microwave or the ceiling of the unit. The wave guide is a metal shield with a single securing screw.
Remove the securing screw with a Phillips screwdriver. Slide the wave guide down, disengaging the upper corners from the microwave. Remove the wave guide completely from the unit.
Clean the area around the hole that the wave guide covers, using a damp rag. This area must be clean so the wave guide seals the hole completely.
Insert the top corners of the wave guide into the two slots on the inside of the microwave. Align the mounting hole on the wave guide with the mounting hole on the microwave. Secure the wave guide with the screw.
Place the roller ring and plate back in the microwave. Shut the microwave door and plug the power cord into the wall outlet.