Photos change drive letter in PE13 and PE18 trial

After trying the PE2018 trial, in both that version and in my original PE13 the photos location changes from C: to M:.  The photo thumbnails will then turn grey and i am unable to do anything with the photos.  Even trying to reconnect photos does no good, as PE says no missing photos.  I have tried many different things, including CCleaner and removing ALL adobe products and reinstalling PE13.  If i import from my external HD, E: the organizer has no problem keeping track of those photos.  If anyone has a suggestion oh how to cure this adobe error, please reply.