How to fix error error-ds-cant-tree-delete-critical-obj in Windows 11

Solution Steps

1. 1 Open Active Directory Users and Computers: Press Windows key + R, type 'dsa.msc', and press Enter. This opens the AD management console.
2. 2 Navigate to the object you're trying to delete. Right-click on it and select Properties. Go to the Object tab and check if the 'Protect object from accidental deletion' checkbox is selected. If it is, uncheck it and click OK. This is the most common cause of this error.
3. 3 After unchecking the protection, try deleting the object again. If it still fails, you may need to use the command-line tool 'ntdsutil' to force deletion. Open Command Prompt as administrator and run 'ntdsutil'.
4. 4 In ntdsutil, type 'activate instance ntds' and press Enter. Then type 'files' and press Enter. Finally, type 'delete object ' (replace with the actual DN) and press Enter. This is a more forceful method and should be used with caution.
5. 5 If the object is a domain controller, you may need to demote it properly using the Server Manager. Go to Server Manager, click on Tools, and select Active Directory Domain Services. Follow the prompts to demote the domain controller, which will remove it safely.