Transfer FSMO or flexible single master operations roles

1. Open command prompt
2. type ntdsutil
3. type roles
4. type connections
5. type the name of the server in which you wish to transfer the roles to connect to server <ServerName>
6. type quit
7. type transfer schema master
8. type transfer domain naming master
9. type transfer pdc
10. type transfer rid
11. type transfer infrastructure master

You can now demote your old DC if you wish by running dcpromo