I am currently working on a project which includes replacing several 2003 servers with 2008 servers and migrating an exchange 2003 server to exchange 2010. When I started the domain consisted of 4 2003 servers, one of which is also the exchange 2003 server. All 4 2003 servers were DCs. I believe this network never had a 2000 server but I can't guarantee that for certain.
I have added 4 2008 r2 servers to the network. 3 have been promoted to DCs, the 4th is to become my Exchange 2010 server. I have since demoted 2 of the 2003 servers. Now for my problem.
When I attempt to install Exchange 2010, during the initial prep phase it errors out with the message "Error: the forest functional level of the current active directory forest is not Windows 2003 native or better". I have verified that my AD is 2003 by attempting to raise the level again - at both remaing DCs - and both reply that the AD is raised as far as it can go (2003). I have also verified in Exchange System Manager that the AD is in native mode. I believe that I would not have been able to promote my 2008 R2 servers to DCs if this was not the case.
Where else can I look for anything that would confuse the Exchange 2010 installation routine?