Windows Server 2003 (sometimes informally referred to as Win2K3, or just 2K3) is a server operating system produced by Microsoft and released on April 24, 2003. It was a successor of Windows 2000 Server and incorporated some of Windows XP features. 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. Windows Server 2003's kernel was later adopted in the development of Windows Vista.