SYMPTOMS
When an administrator uses Active Directory Users and Computers Management Console to remove a computer object, the administrator may receive the following error message:
The object YOURCOMPUTER (or some of the objects it contains) cannot be deleted because Critical Directory Service System objects cannot be deleted during tree delete operations. The tree delete may have been partially performed.
Microsoft recommends that you remove a Windows 2000 Domain Controller from a domain by using the DCPromo.exe tool to demote it. An administrator might need to remove an account for a Domain Controller that is no longer present.
RESOLUTION
To resolve this issue, delete the Domain Controller's server object from Active Directory Sites and Services Management Console. This also deletes any connection objects.
For additional information about deleting a server object, click the article number below
to view the article in the Microsoft Knowledge Base:
216364 Domain Controller Server Object Not Removed After Demotion
If you continue to experience this issue, you need to remove the connection object for the Domain Controller by using NTDSUTIL.
For additional information about using NTDSUTIL to remove the connection object, click the article number below
to view the article in the Microsoft Knowledge Base:
216498 Removing Active Directory Data After an Unsuccessful Demotion
After you remove the Server object and any connection objects, you can delete the computer object in Active Directory Users and Computers.