I couldn't find any advice or help on this particular topic, even though I was pretty sure I knew how to do it. The task was to reinstall a domain controller with it being the only domain controller in the domain. Meaning that when it goes down, there will be no authentication between computers in the network.
The obvious way would be to install another DC so that it can be up while the other is down. But for this situation, another computer is out of the question. So the best way to do this is to completely remove the hard drive and put in a brand new one and install a fresh new version of the OS. After the OS has been installed and updated, perform a dcpromo and make all settings exactly the same as the old DC.