ArcMap has the bad habit of forgetting to unlock files that you remove from a project. I have lost hours, as the only solution to remove unwanted locks seemed to be shutting down ArcMap, modifying the file, then restarting ArcMap (that takes at least a minute to load each time). Nothing seemed to help until I came across “Unlocker” by Empty Loop.
Once Unlocker installed, just left-click the file you want to edit and release it from ArcMap’s lock.
