I recently blogged on the process to install a new domain controller in Windows 2012 (available here). As part of addition of a few of my new Windows 2012 domain controllers I accidentally installed a domain controller as datacenter edition of Windows Server 2012 instead of standard edition. To address this situation I decided to demote it, remove the domain controller and create a new Windows Server 2012 standard edition server to become a domain controller. The following is the process that I used to remove the existing Windows 2012 domain controller.
From the Server manager, I accessed the manage option and chose to Remove Roles and Features.
This resulted in an error but brought me where I needed to be to demote the domain controller as shown below:
The demotion process was intuitive / each of the screens involved are shown below.
After the process completed, it was rebooted to complete the process.
I validated the membership for domain controllers in AD users and computers and validate that the DC was no longer listed.
After a reboot the Active Directory Domain Services and DNS Server roles can now be removed.
Another reboot completed the removal of the features.