The logical structure of the network is defined by forests and domains, with domains organized into domain trees in which subdomains (called child domains) can be created under parent domains in a branching structure. Domains are logical units that hold users, groups, computers, and OUs (which in turn can contain users, groups, computers, and other OUs). Forests are collections of domain trees that have trust relationships with one another, but each domain tree has its own separate namespace. Aspects of the physical structure include sites, servers, roles, and links.

An Active Directory always begins with a forest root domain, which is automatically the first domain that you install. This root domain becomes the foundation for additional directory components. The domain is the starting point of Active Directory. It is the most basic component that can functionally host the directory. Simply put, Active Directory uses the domain as a container of computers, users, groups, and other object containers. Objects within the domain share a common directory database partition, replication boundaries and characteristics, security policies, and security relationships with other domains. The process of creating the forest and domain structure is centered on the use of the Active Directory Installation Wizard, which is also known as the dcpromo utility.

The first step is to install Windows Server 2003 as a member server or a stand-alone server. Next comes the decision process leading to the installation of a DC. Essentially, there are two reasons to install a DC:...