like this
PHP Code:
define('FORBIDDEN_EXTENSIONS','(index[0-9]+\.html|guestbook|\.(cgi|php|asp|pl|rm|ico|cab|swf|css|gz|z|tar|zip|tgz|msi|arj|zoo|rar|r[0-9]+|exe|bin|pkg|rpm|deb|bz2)$)');
remove space
remove cgi|php|asp|pl| if you want index of links end with that extensions
you need to go admin update - delete links you no want - run the cleans - edit FORBIDDEN_EXTENSIONS - index