A mode of operation for domain controllers in Microsoft Windows 2000–based networks. Windows 2000 domain controllers are computers that contain a writable copy of Active Directory. You can convert a Windows 2000–based server to a domain controller by running the Active Directory Installation Wizard on that machine.
You can run Windows 2000 domain controllers in either of two modes:
By default, Active Directory is installed on a Windows 2000 server in mixed mode. You can change a domain controller from mixed mode to native mode, but not vice versa. Use the administrative tool Active Directory Users and Computers to perform the change.