Didn't you ask this before?
What do you mean you have a public computer?
What would you do with the knowledge of the changed files etc?
Do you want software that will reset the PC back to a preset configuration on each reboot undoing any changes? If so, Goback from click here can do that.
If you give us more information, like what the PC is used for, what you are afraid of loosing, who's using this PC and what you want to do when you find out what changes have been maybe we can help more...