A domain mode for running Microsoft Windows 2000 domain controllers that is incompatible with domain controllers running the earlier Windows NT operating system.
You can use domain controllers running in native mode only to authenticate users on a pure Windows 2000–based network.
If your network contains a mixture of Windows 2000 and Windows NT computers, you should configure your Windows 2000 domain controllers to run in mixed mode so that they can interoperate with Windows NT domain controllers.
If you plan to use native mode, all domain controllers must be running Windows 2000 and must be configured to run in native mode, but member servers and client workstations can run either Windows 2000 or Windows NT.
Native mode gives you more options than mixed mode regarding types of groups. Specifically, you can use global groups, domain local groups, and universal groups, and you can nest them to any degree. Running in mixed mode means that universal groups are not available, and you can nest global groups only in domain local groups and only to one level of nesting.
Windows 2000 domain controllers install in mixed mode by default. You can use the administrative tool Active Directory Domains and Trusts to change your domain controllers from mixed mode to native mode. If you change a domain controller to native mode, you cannot change it back to mixed mode, so don’t make the change until all your domain controllers are running Windows 2000.