locking down desktop

We have a user in a remote office that is prone to installing unauthorized software on his machine. What is the best way to prevent him or anyone from installing any program on his machine? The machine in question in running Windows 2000 Pro Sp4 and is not part of the Domain. It is a stand alone machine that connects to the main office via a terminal server connection I am aware of the ability to create security policies on XP machines. Thank you.