Before you deploy Active Directory in your organization you should ensure that the server hardware that you are using meets the minimum requirements to run Active Directory. This video looks at the hardware requirements needed by Active Directory to run in your organization.
Listed below are the minimum requirements. Whenever possible you should try to exceed these values as the minimum values will not give you the best Windows experience. To ensure you have enough room for the Active Directory database and room to expand, you should have at least a 100GB hard disk.
64bit Hardware Windows Server 2008/R2
1.4 Ghz CPU
1.3 Ghz dual core on Windows Server 2008 R2
64GB hard disk space
32bit hardware Windows Server 2008
512mb ROM (2GB recommended)
32GB hard disk space
32bit is not supported for Windows Server 2008 R2
Active directory also requires DNS Infrastructure to work. Certain DNS records need to be created in order for the clients to find domain controllers.