The schema master is Windows Server 2003 R2 with SP2 and we plan to extend the schema to R2. We have several Windows Server 2003 SP1 and SP2 servers that are planned to become Domain Controllers and we have 1 2000 SP4 Server that is already a DC. After we extend the schema so we have to upgrade all these server to R2, or will the domain function just fine without doing so. Also, will upgrading the existing 2003 SP2 servers to R2 require an additional license for the R2 license (purchase)? The 2000 DC is going away before this switch over so that is not an issue. Thanks!