Windows Server 2003 (sometimes informally referred to as Win2K3, or just 2K3) is a server operating system produced by Microsoft, released on April 24, 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on December 6, 2005. Its successor, Windows Server 2008, was released on February 4, 2008. It is based on Windows XP, basically becoming an enhanced version of XP.