Open the projector and replace the bulb with the good one. When you pick up the slide, a timed sequence starts, and it is very short, as you will find out. If you try to put the slide in the projector, you get nabbed.
Pick up the slide, and click on it immediately to put it into inventory. Close the projector.
Step back twice, turn right toward the cabinet.
Step forward twice to hide in the cabinet, being careful not to click on the Acme box.