I received the following message today when trying to delete a computer object from Active Directory:
Object %COMPUTERNAME% is a container and contains other objects. Are you sure you want to delete object %COMPUTERNAME% and the objects it contains? This operation could take a long time if %COMPUTERNAME% contains a large number of objects.
To determine which sub-objects this message referred to, I opened Active Directory Users and Computers.
I then selected View > User, Groups, and Computers as Containers.
I found the computer object in question, and expanded the plus sign to the left of the object name. The sub-object was named msmq, and a Google search showed me it was a part of Microsoft Message Queuing.
Since this computer was about to reimaged, I didn’t have any problem with deleting the computer object, along with it’s msmq sub-object.