Hold on to your hat. This could be a bumpy ride!


Here is the Microsoft propaganda on the subject:

Installing an Additional Domain Controller

Prepare a Windows 2000 or Windows Server 2003 Domain for a Domain Controller That Runs Windows Server 2008 or Windows Server 2008 R2

Prepare a Windows 2000 or Windows Server 2003 Forest Schema for a Domain Controller That Runs Windows Server 2008 or Windows Server 2008 R2

Windows Server 2008 R2: Forest-Wide Updates

Here is an article from a blog that seems pretty well written:

Introducing your first Windows 2008 R2 Domain Controller