- You would first want to move all of the FSMO roles over to a single DC that is in the child domain. You can use the NTDSUTIL tool to perform this function.
- Run DCPROMO on all DC's EXCEPT THE ONE HOLDING THE FSMO roles for the child domain.
- When all of the other DC's are demoted, remove them from the domain.
- Run DCPROMO on the final DC in the child domain. This should remove the objects from the parent domain. However, there are cases where this will not work correctly. So, you will need to check the Active Directory Sites and Services to make sure that the replication objects have been correctly removed. If the objects are not removed, you will have to remove them manually. Microsoft has a white paper that I have used serveral times that details this nicely:
How to: Remove orphaned domains from Active Directory
Generally, all will go well as long as you moved all of the FSMO roles to a single server prior to demotion.
This was first published in May 2004