If this is a primary domain controller you must promote it to a Domain Controller and after there is at least one more replica ...

If this is a primary domain controller you must promote it to a Domain
Controller and after there is at least one more replica domain controller
in the domain, demote this computer to a non-DC server, rename it, and then
promote it back to a domain controller by using the Active Directory Domain Services
Installation Wizard. On other domain controllers running Windows NT 4.0,
modify the name, if necessary, prior to upgrading to Windows 2000.