Did you set up separate profile accounts on the computer?

You can set up as the admin, and others can be limited users or "guest"
I have a post on it here- with how to do it links -
http://neurotalk.psychcentral.com/thread40958.html

guest would have the most restrictions
limited users can make some changes on their own profile/account but not many computer wide changes.

I have 5 user accounts set up on my computer for family members and I have the admin account.