I opened a slideshow file, probably made with Powerpoint, and it went full screen and is playing Glenn Miller's in the Mood over and over. Strangely, I can't see any of the images being played and it's just a blank white square in the middle of the fully blacked out screen. What do I press to get this to stop and the program to close? I've tried esc., delete, and all sorts of combinations of those keys with the control button, shift, alt, etc. What's the secret abort button?