Windows Server 2008

Windows Server 2008, released on February 27, 2008, was originally known as Windows Server Codename "Longhorn". Windows Server 2008 builds on the technological and security advances first introduced with Windows Vista, and is significantly more modular than its predecessor, Windows Server 2003. At the Professional Developers Conference (PDC) 2008, Microsoft announced Windows Server 2008 R2, as the server variant of Windows 7. Windows Server 2008 R2 ships in 64-bit (x64 and Itanium) only.
Windows Server 2008 ships in ten editions:
Windows Server 2008 Standard Edition (32-bit and 64-bit)
Windows Server 2008 Enterprise Edition (32-bit and 64-bit)
Windows Server 2008 Datacenter Edition (32-bit and 64-bit)
Windows HPC Server 2008
Windows Web Server 2008 (32-bit and 64-bit)
Windows Storage Server 2008 (32-bit and 64-bit)
Windows Small Business Server 2008 (64-bit only)
Windows Essential Business Server 2008 (32-bit and 64-bit)
Windows Server 2008 for Itanium-based Systems
Windows Server 2008 Foundation Server