You want to promote a server to a domain controller. You may need to promote a domain controller to either initially create a domain in an Active Directory forest or add additional domain controllers to the domain for load balancing and failover.
Run dcpromo.exe from a command line or via Start Run and answer the questions according to the forest and domain you want to promote the server into.
Promoting a server to a domain controller is the process where the server becomes authoritative for an Active Directory domain. When you run the dcpromo program, a wizard interface walks you through a series of screens that collects information about the forest and domain to promote the server into. There are several options for promoting a server:
Promoting into a new forest (See Recipe 2.1)
Promoting into a new domain tree or child domain (See Recipe 2.3)
Promoting into an existing domain
You can automate the promotion process by running dcpromo during an unattended installation. See Recipe 3.4 for more details.
Recipe 2.1 for creating a new forest, Recipe 2.3 for creating a new domain, and MS KB 238369 (HOW TO: Promote and Demote Domain Controllers in Windows 2000)