Security on Directory

Hi all, I have developed a authentication system using php4 and mysql running on web apache 1.3. This is fine for authorising the php files but not for any images or external files which I want secured. I have tried .htaccessing a directory and using php to access the folder but to no joy as still asked for the password. Has anyone got a solution? I've heard of mod_auth_mysql but I do not have this option, I am running the module version of apache and have used the php basic authentication with no problems. However can this variable be passed to a .htaccess file. I would be so greatful if someone could help thank you in advance