Windows Server 2008
Windows Server 2008, codenamed "Longhorn Server", is the fourth release of the Windows Server operating system produced by Microsoft as part of the Windows NT family of the operating systems. It was released to manufacturing on February 4, 2008, and generally to retail on February 27, 2008. Derived from Windows Vista, Windows Server 2008 is the successor of Windows Server 2003 and the predecessor to Windows Server 2008 R2.
Windows Server 2008 removed support for processors without ACPI. It is the first version of Windows Server that includes Hyper-V and is also the final version of Windows Server that supports IA-32-based processors (also known as 32-bit processors). Its successor, Windows Server 2008 R2, requires a 64-bit processor in any supported architecture (x86-64 for x86 and Itanium).
As of July 2019, 60% of Windows servers were running Windows Server 2008.