Installations of Office 2013 may not allow COM add-ins to register successfully

By Amber Mertes

With Office 2013, theAdd-In Designer (msaddndr.dll) was removed.

As a workaround, you may reinstall the VB6 solution for the add-in after you install the MSI version of Office 2013. Copy MSADDNDR.DLL from a working machine and register it on the Office 2013 machine using REGSVR32.

From "Changes in Office 2013" -  http://technet.microsoft.com/en-us/library/cc178954.aspx