I have an environment running Windows 2003 and Exchange 2003 only (no Windows 2008 or Exchange 2007 servers currently) and we are looking to upgrade one or more servers to Exchange 2007. In doing so, I need to run the necessary setup commands to prep the AD. My question is: are there any ramifications for existing Exchange 2003 servers when these setup prep is run that might break Exchange 2003 servers? I understand that these steps make substantial changes to the AD. We only want to upgrade one server for now, and leave the others at Exchange 2003 for now, so it is important that we do not break Exchange 2003 while upgrading to Exchange 2007.