Udcofficeaddin2000.dll -

HKEY_CURRENT_USER\Software\Microsoft\Office\<OfficeVersion>\Word\Addins\ HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\<OfficeVersion>\Word\Addins\ Delete any key referencing UDC.OfficeAddin2000 or similar.

If you still experience issues after following this guide, provide your (e.g., Office 365 64‑bit) and Windows version for further diagnosis. udcofficeaddin2000.dll