Problem with public computer?

Ok, I am about to join a group that deals with sensitive information. The only access I have to the internet is through public use. I recently learned that the screen of the public access computers I am using are able to be veiw by the admin of the computer sys. I knew they did this at schools, and I knew it was possible on any public access computer. I was wondering if there was a portable program to disable this, or setup a screen that tells what organization I with and that this information currently on MY screen is sensative.