Locking a system

I’m running NT4 server and w2k clients. I have one client system that I want to prevent other users from being able to log on.

For example, if I’m absent it will not allow other users to log on to my machine.

I know in the User Control panel you can assign users to a computer, but is there a way you can assign a computer to a user and only that user?

Can this be done without additional software?

Phill