Mixed Mode: Permits domain controllers executing both Windows 2000 and prior versions of Windows NT to co-exist in the domain. In mixed mode, the domain features from prior versions of Windows NT Server are still allowed, whereas some Windows 2000 features are disabled. The Windows 2000 Server domains are installed in the mixed mode by default. In mixed mode the domain might contain Windows NT 4.0 backup domain controllers existed. Nested groups are not supported in the mixed mode.