Windows Server 2000
Windows 2000 is a line of operating systems produced by Microsoft for use on business desktops,notebook computers, and servers. Released on February 17, 2000, it was the successor to Windows NT 4.0, and is the final release of Microsoft Windows to display the "Windows NT" designation. It was succeeded by Windows XP for desktop systems in October 2001 and Windows Server 2003 for servers in April 2003.
Four editions of Windows 2000 were released: Professional, Server, Advanced Server, and Datacenter Server. Additionally, Microsoft sold Windows 2000 Advanced Server Limited Edition and Windows 2000 Datacenter Server Limited Edition, which were released in 2001 and run on 64-bit Intel Itanium microprocessors. (Source: Wikipedia)