Delete Failed DCs from Active Directory

My customer's AD environment ran into problems few days ago. Currently they have 4 production domain controllers, but they booted up an old domain controller which has been down for more than 2 months and causing the client to face slow login issue.

Immediately they shutdown the problematic DC and requested us to decommission the failed DC for them.

By right, running "dcpromo" on the failed DC to decommission it is the fastest and easiest way to achieve the goal, but somehow dcpromo doesn't work as expected, so I use the command "ntdsutil" to accomplish my mission.

"ntdsuitl" is a very useful and powerful command, click here to read more about it about how to use "ntdsutil" to decommission a failed DC.