Windows Server 2008
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 x86-based processors (also know as IA-32-based or 32-bit processors). Its successor, Windows Server 2008 R2 requires a 64-bit processor in any supported architecture (x86-64 for x86 and Itanium).