How can I recover a bad conf parition when the web interface says my HD is "not formatted"?

If you have erased your conf parition but you have a made a backup of the files (by a simple tar czf /share/hdd/conf/*), when you restore the files, the HD won't be recognized anymore...

The solution is to recreate the two hidden files that you haven't saved...

If your conf parition isn't mounted yet, mount it (mount /dev/sda2 /share/hdd/conf)

The commands are:

  
        touch /share/hdd/conf/.dongle
        chmod 0666 /share/hdd/conf/.dongle
        touch /share/hdd/conf/.htpasswd
        chmod 0644 /share/hdd/conf/.htpasswd
  

Now you must fill the .htpasswd file by a password generated by the htpasswd provided by Apache... search for htpasswd on Google for more information...