Windows Server 2008 Hardware Requirements
Before you arrange and use Active Directory, you need to install Windows Server 2008. Start by making sure that the machines you plan to use as domain controllers are capable of running the operating system. This list shows you the minimum and recommended hardware levels for Windows Server 2008:
Component                                                                                Requirements
Processor                                                                 1 GHz (x86 CPU) or 1.4 GHz (x64 CPU)
Memory                                                                    512MB required ; 2 GB or higher recommended.
Hard diskÂÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 10 GB required. 40 GB or more recommended.
Video                                                                         Super VGA or higher video card and Monitor.
Hardware                                                  Must be on the Windows 2008 Hardware Compatibility List.