I would like to upgrade my 1.5.7 wiki to version 1.6.6 but i have ONLY ACCESS TO: 1) the files through FTP 2) the database through phpmyadmin

I was thinking of upgrading through a web-based install, but it seems that i have to make the 'config' subdirectory writable by the web server. Is there a way to upgrade without having to make something writable on the webserver or i am missing something?

thanks! Jan