This plugin is pretty simple. Though for a PHP4 driven site, currently only FTP archiving is available. It is highly recommended that to get the most out of this plugin & to do enable the best data protection; you use an FTP account that is truly, meaning separate domain name (and more importanyly, separate a IP address).

It's a good idea to store the following two items on your own, (in the same place as the files above).
Your copy of WordPress:
Your copy of wp-config.php For security purposes this file is not backed up!