I have a 2003 domain that has been running for years--no real issues. Recently started thinking of replacing the 2003 Enterprise Edition with Server 2012 Standard Edition. Installed 2012 as a VM on Hyper-V 2012, which also hosts the 2003 enterprise as a VM. Did all the 2012's updates and then added the AD role (rebooted) +and tried to join it to the 2003 domain--fails. Please see attached file/pictures for details 1) 2003 "functional domain level" is set to 2003 (highest possible for 2003) 2) On the 2012 server in server manager I can click on the "promote this server to a domain controller", add the required credentials, it finds the existing domain but then errors out 3) the error is "verification of replica failed, the forest functional level is 2000, to install 2012 the functional domain level must be 2003 or higher (but it is 2003). 4) ran dcdiag on 2003 server and all tests passed. Tried several suggestions from online searches (removed DNS on 2003, rebooted and reinstalled it) and none are working. Help please-thanks.