William, Lacking the knowledge of how to accomplish this upgrade is exactly why I am here, asking questions. Knowing the definitions of a collection of acronyms is not going to help us get this upgrade accomplished. I have read the Microsoft articles, and they are rather comprehensive, but none tell a person exactly what needs to be done to accomplish an upgrade from Exchange 2000 running on the PDC/ADS server which is also running on Windows Advanced server 2000. If Exchange 2003 needs a Windows 2003 ADS, then we have a delima, don't we? Let me ask you this...will Exchange 2000 run under on a Windows 2003 PDC? If so, then shouldn't we upgrade the server to Windows 2003 first? Thank you, Bjorgen