Locking a computer

Hi all!
I?m trying to put a PC in an open zone where people can only run one application. I?ve used GPO to hide drives and stuf like these but someone allways gets a way to close that app, create icons, try to open programs, etc…

What can i do to make a PC boot, load a user profile, start that program and prevent “show desktop”, start any programs, viewing any drives.

Can you help me?

Thank you