In ignorance,  I copied back a .pab file after re-installing Windows
and Office XP.  I did not know I should have exported and imported it.

This created a second 'contacts' leaving the first one in an invalid
state, hence I 'lost' the ability to open contacts when composing, but
'worked around' this by telling Outlook to look at the second contacts
folder first.

However I cannot find any way of totally deleting the invalid
'contacts' 'folders' from the list.  Is there any way of doing this?