deniyng user to mess up pc

Hello,
I'm developing an application that will collectdata through a touchscreen
monitors.
Essentailly it's an application which administer questionnaires to subjects
in my private practice.
For privacy, the user will be alone while answering the questionnaire.
Even if I make the form to run in full screen mode and even if I make them
pop up and modal, the user has stil a chance of touching the "start" button
at the bottom of the window and by that way to go around and mess up the
computer by deleting anything he/she wants to.
I have managed to disable the keyboard but cannot immagine hot to drive the
user not to be able to act on the start menu. I can hide the taskbar, but I
was looking for some better solution.
Hoping to have well explained what I'm looking for, thanks in advance.

Rocco

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