I'm getting "Restricted access" when i tried to install Joomla

Installation Joomla 1.0.11 or 1.0.12 I was getting "Restricted access" after uploading all installation files to my hosting provider. after trying to set some other rights to the files, i had no success. finally i debugged a little the process and with a define( '_VALID_MOS', 1 ); placed in installation/index.php as the first php code line solved the problem i suppose with it it's not really secure, but you have to delete the installation folder anyway..