PTB exiting midscreen

So, I am using PTB to show visual stimuli via a touch screen. It is a simple 3AFC task, the stimuli are drawn on the screen and they stay there till one of the options is selected. The only way one can quit the experiment is by pressing the ESC key which the participant does not have access to (they have access only to the touchscreen).

Sometimes, the participant touches the screen randomly (and not just the stimulus) and the screen goes to the Windows desktop while PTB keeps running in the background. The problem is that the participant could get past PTB and go to Windows, which should never be the case.

Would love to hear some solutions!

Is your PTB window full screen?

Yes, it is full screen.

I assume you use Psychtoolbox touchscreen functions, as demonstrated by, e.g., MultiTouchMinimalDemo.m. My only free advice is to switch to Linux, for its superior touch input support, at least on typical run of the mill (not too exotic) touch screens.

Beyond that, for up to 30 minutes of paid advice on Windows, help PsychPaidSupportAndServices tells you the procedure.