Folder is ready for archiving
Solution 1:
It sets the "archive" attribute on the folder.
Wikipedia explains:
On Windows and OS/2, when a file is created or modified, the archive bit is set, and when the file has been backed up, the archive bit is cleared. It is by use of the archive bit that incremental backups are implemented.
You can view whether the archive attribute is set from the command line with attrib [file] (an A will be present if it's set), and set or remove it with attrib +A [file/folder] or attrib -A [file/folder].