Windows NT 4.9

Windows 2000 metung yang dakal a pamag-abul ning Windows NT operating system a ini-develop ning Microsoft at atin yang pamagtutuk dignan kareng negosyo. Ityang direktang sumunod ya keng Windows NT 4.0, at inrelease ya king pabrika king Disyembre 15, 1999,[2] opisyal a inrelease king retail king Pebrero 17, 2000 para kareng eganaganang bersyon, at king Setyembre 26, 2000 para keng Windows 2000 Datacenter Server. Iti ya ing pangunang operating system ning Microsoft a orientadong negosyo hasta king pagpasalikut ning Windows XP Professional king 2001.