We're using a powerpoint presentation on a touchscreen that allows users to "click" into various boxes to get all sorts of information.

We need to prevent users from ending the presentation, and returning to the desktop though.

If they can get back to the desktop, they'll be able to cause all sorts of mischief - we want to avoid this obviously

We have removed the keyboard and mouse, but is there any facility in powerpoint, or any third party add on that can prevent a powerpoint presentation from ending?