[Michael Polda]

This is an old post so I don’t know if anyone will see this. The above solution worked, but only within PowerPoint itself. In other words, PowerPoint slides are mirrored on the projector. However, if I cmd-tab to another application the projector is NOT mirroring and I see only the wallpaper for a second monitor even though the display setting in System Preferences is set to mirror. It’s like PowerPoint overrides the system preference and turns off mirroring then fakes it by outputting slides to both monitors. Since I often switch back and forth between apps during a presentation this doesn’t work. I’ve been forced to open my files with Keynote as a workaround. Any suggestions?