On Sun, 21 Sep 2014 11:28:31 +0100, Joe User wrote:

OK, here's the problem.

I'm a volunteer for a local charity. Recently we received a grant to
replace our aging equipment and got 4 spanky new computers running
Windows 8.1. A wide range of people have access to these machines
including the elderly, the homeless, the unemployed the disadvantaged,
dispossessed, and other groups on the outskirts of society. We have no
idea who's using the machines at any moment as I and the other
reasonably competent volunteer can't be there all the time. We *know*
someone has been trying to get into the guts of the things and now we
are beginning to understand how they might be doing it.

What is out solution?

Maybe kiosk mode would help. You allow access to specific applications and
AFAIK that's all that anyone has access to.

http://blogs.technet.com/b/canitpro/archive/2013/12/17/step-by-step-enabling-kiosk-mode-in-windows-8-1-via-assigned-access.aspx