For various reasons, there are times when Active Directory may encounter a situation where multiple objects appear. The duplicates will be named with a CNF:[GUID] on the end of the name.
Here is an excellent Microsoft blog post with an explanation of why it happens and some simple commands to find these objects. It is an issue we encounter at times with Configuration Manager boundaries and slow AD replication, but could happen for many other object types also.
For a slightly simpler method, here is my approach to using AD Users and Computers to find and delete them.
In this example I am looking specifically in the “System Management” container, but you could apply it at the root of the tree to find any duplicates
- Create a new saved query in AD Users and Computers
- Set “System\System management” as the Query root (you need “Advanced view” enabled)
- Define a “Custom Search” and in the Advanced tab enter (cn=*cnf:*)
- Now just refresh the query to find the duplicates, select and delete