This should do it if the 7star.php file is in the root directory of your website. It should work, I tested it.
PHP Code:
Options +FollowSymlinks
RewriteEngine on
RewriteRule ^7star.php /7STAR.php [r=301]
This will redirect it from 7star.php to 7STAR.php. Sometimes you'll need to leave the "Options +FollowSymlinks" out. This depends on the server.
I hope that helps.
EDIT: Of course this goes into a .htaccess file placed in the root directory of your public folder.