Here are the high level steps which you can use to upgrade the Active Directory.
Note – Windows Server 2008 R2 includes a 32-bit version and a 64-bit version of Adprep.exe. The 64-bit version runs by default. If you want to run one of the Adprep.exe commands on a 32-bit computer, use the 32-bit version of Adprep.exe. It is called Adprep32.exe. In Windows 2008 R2, it is located in the \Support\Adprep folder.
2. Verify the schema version
Note – You can verify the schema version using dsquery * cn=schema,cn=configuration,dc=sivarajan,dc=com -scope base -attr objectVersion command. The following table lists the Active Directory Schema and the corresponding Object Version:
|Active Directory||Object Version|
|Windows 2003 R2||31|
|Windows 2008 R2||47|
|Windows 8 Beta||52|
|Windows 2012 R2||69|
***ObjectVersion 39 – Please refer http://blogs.technet.com/b/askds/archive/2011/07/15/friday-mail-sack-peevish-nediquette-edition.aspx
3. Install a new server with correct version of OS and join this server to the existing domain.
4. Perform DCPRMO on this server and select Additional Domain Controller for an existing Domain option.
Reference PowerShell – http://technet.microsoft.com/en-us/library/hh472162#BKMK_PS
Note – If you are using Active Directory Integrated (ADI) DNS, it will get replicated as part of the Active Directory replication.
Note – You can identify the FSMO role DC information using Netdom /Query FSMO command.
Reference FSMO – http://support.microsoft.com/kb/324801
6. You can remove (demote) a domain controller using DCPROMO command and again, since WS2012 also possible with PowerShell.
Reference PowerShell – http://technet.microsoft.com/en-us/library/hh472163#BKMK_RemovePS