Microsoft has replaced Windows 2000 Server products with Windows Server 2003 , and Windows 2000 Professional with Windows XP Professional . Windows Neptune started development in 1999 , and was supposed to be the home-user edition of Windows 2000 . Although Windows 2000 is the last NT-based version of Microsoft Windows which does not include Windows Product Activation , Microsoft has introduced Windows Genuine Advantage for certain downloads and non-critical updates from the Download Center for Windows 2000 .