Posted by: Jason Tramer
DC, dcpromo /forceremoval, ntdsutil
There are times when a DC has to be removed by force. It’s really not that hard a quick dcpromo /forceremoval will do it for you. Now comes the tricky part, you have to remove the metadata manually out of AD.
Here is a really great article for this:
This becomes doubly important if you want to ever re-promote the server back to the domain. Without removing the metadata it will not allow you to re-promote.