Deleting a reference in PDM window

Hi,
How do you get rid of an "obsolete" reference in the PDM? The filewas deleted by hand, in an incorrect way - through windowsexplorer, but the reference is still there and anything I try todo, including to even change projects, comes back as an operationfailed.. Help.. can i log on as Admin and get rid of it some way??

-TimSolidworksWorkgroup Pdm