You want to create a new forest by creating a new forest root domain.
126.96.36.199 Using a graphical user interface
Run dcpromo from a command line or Start Run.
On a Windows 2000 domain controller:
On a Windows Server 2003 domain controller:
188.8.131.52 Using a command-line interface
dcpromo can also be run in unattended mode. See Recipe 3.4 for more details.
The act of creating a forest consists of creating a forest root domain. To do this, you need to use the dcpromo executable to promote a Windows 2000 or Windows Server 2003 server to be a domain controller for a new domain. The dcpromo program has a wizard interface that requires you to answer several questions about the forest and domain you want to promote the server into. After dcpromo finishes, you will be asked to reboot the computer to complete the promotion process.
2.1.4 See Also
Recipe 2.3 for creating a domain, Recipe 3.1 for promoting a domain controller, Recipe 3.4 for automating the promotion of a domain controller, and MS KB 238369 (HOW TO: Promote and Demote Domain Controllers in Windows 2000)