If you have a domain with Windows 2000 Server or Windows Server 2003 with Active Directory installed on it, and are planning to install a Windows “Longhorn” Server domain controller to the network domain, you will need to update the schema on the current domain controllers before it’ll work. If you are going to perform an unattended installation, you’ll have to do this on the domain controllers before you actually install Windows “Longhorn” Server and Active Directory. You can do this by updating the schema on the domain controllers that either host the schema master or infrastructure master. If you are not going to install Windows “Longhorn” Server, please do not update the schema for the sake of it.

 To prepare a domain forest:

1. Logon to the computer which runs as the schema master as a Domain Administrator or Enterprise Administrator.
2. Copy what’s in the \sources\adprep folder on the Windows “Longhorn” Server DVD to a folder on the C: drive called schemaupdate.
3. Go to Start and Run (or press the Windows key+R) and type in cmd then press OK.
4. Type in cd c:\schemaupdate then press Enter.
5. Type in adprep /forestprep then press Enter.
6. Allow the installation to continue and the schema to be replicated on the other servers (if applicable)

 To prepare an entire domain:

1. Logon to the computer which runs as the infrastructure master as a Domain Administrator.
2. Again, copy what’s in the \sources\adprep folder on the Windows “Longhorn” Server DVD to a folder on the C: drive called schemaupdate.
3. Go to Start and Run (or press the Windows key + R) and type in cmd then press OK.
4. Type in cd c:\schemaupdate then press Enter.
5. Type in adprep /domainprep /gpprep then press Enter.
6. Allow the installation to continue and the schema to be replicated on the other servers (if applicable)