We still have win 2000 DCs and some 2003. One of my projects for 2010 will be to remove all 2000 DCs and get ready for 2008 DC deployment late 2010 or early 2011. This guide will be a great read for that project.
Upgrading your network operating system requires minimal network configuration and typically has a low impact on user operations. The upgrade process is straightforward, efficient, and allows your organization to take advantage of the improved security that is offered by the Windows Server? 2008 and Windows Server 2008 R2 operating systems.
This guide is intended for use by system administrators and system engineers. It provides detailed guidance for upgrading Windows 2000 or Windows Server 2003 Active Directory domains to Active Directory Domain Services (AD DS) domains that have domain controllers running Windows Server 2008 or Windows Server 2008 R2. For a seamless deployment experience, use the checklists that are provided in this guide and complete the tasks in the order in which they are presented.
Go get the guide @ http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=fa629de2-f4dd-47ac-8d80-3db46b2877a2.
Continued at source?
Upgrading AD Domains to Windows Server 2008 R2 AD DS Domains