I keep getting an error Message when i try to open Lightroom. It states...... "The Lightroom catalog Named 'Lightroom catalog' cannot be opened because another application already has it opened." Then 3 little boxes pop up and one says choose a different catalog , continue or Exit
Use Windows Explorer or Finder to open the folder that contains your catalog. You will see a file in that folder with the .lock extension. That file needs to be deleted, and then you will be able to start Lightroom.