Server 2008 has a neat feature for preventing accidental deletions. It’s enabled by default when creating a new OU, but has to be enabled on users and computers.
To view the status or to enable/disable this feature, head over to ADUC, view and select advanced features. Right click the OU, User or Computer, select properties and view the object tab.
If you try and delete a protected item, you will be greeted with the error message “You do not have sufficient privileges to delete %object%, or this object is protected from accidental deletion.”
This is a handy feature for those extra important users and computers, or simply to prevent silly mistakes at the OU level.