Files In Use dialoge is DANGEROUS - changes suggested
A user may select the checkbox "Shut down computer after completing the operation", so that they can go to bed while the backup completes.
If they did not select this checkbox, when they start the backup they may leave the computer to do something else while the backup completes.
In either case, they may not see the "Files in Use" dialogue, as it is only shown for 180 seconds.
If this dialogue is not seen by the user, then they have every right to believe that the backup completed successfully.
If the "Files in Use" dialogue expires after 180 seconds, then the list of files not backed up should be written into the "File Backup Progress" dialogue and the final message should reflect the incomplete nature of the backup.
For the users who select the checkbox "Shut down computer after completing the operation" the problem should be brought to their attention the next time that they start the software.