Deleting “network” contacts from Windows Live Mail 2012

I run WLM 2012 under Windows 10 (upgraded from Windows 8).  If I view my contacts as a list most are 'from' the address book but several have no entry in the 'from' column.  Those with no entry cannot be edited or deleted.  Several people on the Forum have suggested that they come from Skype, but I certainly don't have them in my Skype address book.  Also, they are not in my gmail contacts list.  I can't think of any other place they might have come from except perhaps they were imported from my last computer when I upgraded.  Any idea (1) how to delete them (2) tell where they come from or (3) stop WLM picking them up from wherever.  The problem is they are all old and some people have changed email address so I now have entries that are just plain wrong.