Microsoft Knowledge Base Article 224390 contains the following summary:
In Microsoft Windows NT, you can automate the installation of a domain controller using unattended Setup, or while performing a normal, attended installation. In Windows 2000, domain controllers are created after setup, even if you are upgrading to Windows 2000. You can also use a script to run the domain controller promotion (Dcpromo.exe) process. It may be useful to combine Dcpromo.exe with unattended Setup to automate the installation of Windows 2000 and the creation of a domain controller. This article describes how to automate the installation of Windows 2000 and the creation of a domain controller.