Why? You have until 10 backups (Options!) See
Look in the FAQ and search backup --> www.rainlendar.net/cms/index.php?option=com_easyfaq&Itemid=26
or in the wiki --> wiki.rainlendar.info/index.php?title=Backup_and_Restore
or in the help:
Backup and restore
To make a backup from your settings, events and tasks you can select the backup menu item from the manager's file menu. The backup will create a zip archive from the necessary files which you can save to some safe place. If something bad happens you can easily restore all the important stuff from the backup file.
Backup doesn't cover events and tasks from Outlook or from the network calendars like Google calendar. Your skins and languages are not backed up either so you need to copy those manually or download them again from wherever you originally got.
Note that when you restore files from a backup file the files will be overwritten. So all your settings, events and tasks will be reset to the ones that are inside the backup. The backup contains absolute paths to the files so you can only restore it to the same computer or one that has all files in the same locations. The backup file is a standard zip archive so you can also restore the files manually from it too.