Windows 2000 has eliminated many of the restarts that were required when making changes in Windows NT.
Changing computer name is NOT one of them.
When you change computer name in Windows 2000, you must immediately shutdown and restart for the change to take effect.
NOTE: It is highly recommended that no other changes are pending. If you are going to change the computer name and join a domain, first change the computer name and restart. Then join the domain.