Error

Joining a brand new Windows 2003 R2 Server to an existing Windows 2003 Active Directory domain generates errors (via dcpromo).

"The version of the Active Directory schema of the source forest is not compatible with the version of Active Directory on this computer."

dcpromo claims that "the forest is not prepared for installing Windows Server 2003." and you're told to run the "Adprep command-line tool to prepare both the forest and the domain."

Solution

What is this silly dialog box talking about?  You are running Windows 2003 Server.  But not R2. =)

Windows 2003 Server R2 contains additional schema updates/extensions that must be applied before an R2 server can become a DC.

Pop the 2nd R2 disc into an active domain controller, and journey into \CMPNENTS\R2\ADPREP.  Run adprep /forestprep and/or /domainprep again, from this updated source.

Useless (obscure/unclear/vague) error messages, anyone?