I am in the process of building out a new Exchange 2003 server running on Windows Server 2003. The OS loaded fine. Domain prep and Forest prep completed with out any problems. I even installed the management tools with out any issues. However when I go to install Exchange I get a message stating that the install cannot continue because “You cannot install this product on a computer running Windows Professional.” Has anyone else seen this on an install? I have a gut feeling that it is caused by one of the “Critical Updates” but I am not sure which one.