We are planning to upgrade our current Infrastructure to the most updated level. Currently we have our Forest Schema in Windows 2003 AD Domain Controller level, Our Exchange Servers are at version 2007, our Identity Management Server is running MIIS 2003 SP2. In our phase 1 planning we are preparing to upgrade the forest schema to Windows 2008 R2 AD Domain Controller level and Exchange 2010 so as to add Windows 2008 R2 domain controllers and Exchange 2010 servers. Once we upgrade the schema level in our forest will it affect MIIS 2003 functionality in any way? We will not be migrating to FIM2010 as of now but will be done later in phase 2 planning.