Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was released to manufacturing on December 15, 1999 and was officially released to retail on February 17, 2000. It is the successor to Windows NT 4.0, released in 1996, and both Windows 2000 and Windows Me were succeeded by Windows XP in 2001.
Four editions of Windows 2000 were released: Professional, Server, Advanced Server, and Datacenter Server; The latter was both released to manufacturing and launched months after the other editions. While each edition of Windows 2000 was targeted at a different market, they shared a core set of features, including many system utilities such as the Microsoft Management Console and standard system administration applications.
Windows 2000 introduced NTFS 3.0, Encrypting File System, as well as basic and dynamic disk storage. Support for people with disabilities was improved over Windows NT 4.0 with a number of new assistive technologies, and Microsoft increased support for different languages and locale information. The Windows 2000 Server family has additional features, most notably the introduction of Active Directory, Which in the years following became a widely used directory service in business environments.
Microsoft marketed Windows 2000 as the most secure Windows version ever at the time; however, it became the target of a number of high-profile virus attacks such as Code Red and Nimda. For ten years after its release, it continued to receive patches for security vulnerabilities nearly every month until reaching the end of its lifecycle on July 13, 2010.