unable to add computers to workgroup manager


Ok so I am trying to add a computer to workgroup manager on Leapord server. But it says the name already exists. I don’t see the computer any where listed. I am using open directory to manage mac labs usernames and password are taken care of by AD.
I went to apples help page and it says to click on system preferences and check mark show all records tab and inspector but still the 2 computers I want to get rid of still do not show. And it will not let me add them …It’s very frustrating. I followed the instructions on this url but I think it’s more for older version