Each time Zip Backup is used it automatically generates a log file. This is stored in the Zip Backup directory and can be viewed by clicking the "View log file" option on the view menu. The time and date the file was generated will be displayed as well as any files that the program was unable to backup, usually with a reason for the failure. The most common reasons files are not included are because the file no longer exists, in which case you should remove that file from your file list, or, Windows prevented the file from being included. If no files are listed then all of the specified files have been included.