Unlocker application was designed to be a very useful Windows Explorer extension allowing users with a simple right-click on a file or folder to easily get rid of error message such as error deleting file or folder, cannot delete folder.
It has many other flavors: Cannot delete file: Access is denied There has been a sharing violation. The source or destination file may be in use. The file is in use by another program or user. Make sure the disk is not full or write-protected and that the file is not currently in use.