Windows Server 2008

Windows Server 2008 is the server counterpart of Windows Vista, which was released on 27 February 2008, a little over a year after its client counterpart. It replaces Windows Server 2003 and was replaced by Windows Server 2008 R2. It was the first version of Windows Server to include Hyper-V and also the last version of Windows Server to support the x86 architecture.

This is the first version of Windows to drop support for systems without ACPI as well as forbidding installations on partitions formatted under the FAT32 file system, as the operating system will not boot on devices that do not meet these specifications. This is the first version of Windows Server that lacks support for systems without ACPI, as it will display a black screen with error messages when launched. Windows Server 2008 drops the ability to upgrade from Windows NT 4.0 and Windows 2000, requiring at least Windows Server 2003/2003 R2.

Naming
Just like its client counterpart, Windows Server 2008 used Longhorn, by exactness "Longhorn Server", as its codename. However, even after Longhorn has been replaced with Vista in 2005, "Longhorn Server" was still used as codename of Server 2008 until its removal in build 6001.16659 in 2007, two years after its client counterpart and a few months after the release of Windows Vista.

The earliest build to identify itself as Windows Server 2008 was build 6001.16606.

Hardware compatibility
Intel CPUs whose microarchitectures are based on Haswell or later are not supported on Windows Server 2008. Numerous issues relating to certain services or applications failing to start on the affected CPUs have been reported by various users, with extreme cases often leading to potential bugchecks. The KB4493471 update contains a new version of the HAL (hardware abstraction layer) that fixes most of these issues.

Windows Server 2003 R2, earlier operating systems and x86 versions of Windows Server 2008 are not affected by the aforementioned problems.

Development reset
These builds are also referred to as Omega-13 builds.