Versions of Windows NT are Windows NT 3.1 , NT 3.51 , NT 4 , Windows 2000 , Windows XP , Windows Vista and Windows 7 . NT was the first fully 32-bit version of Windows , whereas its consumer-oriented counterparts , Windows 3.1 x and Windows 9x , were 16-bit\/32-bit hybrids . Windows 2000 , Windows XP , Windows Server 2003 , Windows Vista , Windows Home Server , Windows Server 2008 , and Windows 7 are based on Windows NT , although they are not branded as Windows NT .