Make sure that the domain and forest are both in the correct mode. I think it’s called native mode, it might be Windows 2000 mode. They changed the names from Windows 2000 to Windows 2003, and it’s been a long time since I’ve looked at a Windows 2000 domain.
You can check the Forest Functional Level, to do this go to <b>Active Directory Domains and Trust</b>, right click the Domain and choose <b>Raise Domain Functional Level</b>, this will let you perform your task. More info <a href=”http://support.microsoft.com/?scid=kb%3Ben-us%3B322692&x=7&y=14″>can be found here</a>.