Windows NT (and windows 2000) boxes have a negotiated computer account name and password. This is so the two computers can establish a security trust releationship. You cannot join an NT/2000 workstation to a domain unless you've got the necessary privileges.

If you are not the administrator of the network, you will most likely need to call the admin before you can join it to the domain. This is standard practice in any windows network, and your company probably already has a procedure in place for handling this situation.