when i going to install DHTML module i got this warning....

user warning: Duplicate entry 'sites/all/modules/dhtml_menu/dhtml_menu.module' for key 'PRIMARY' query: INSERT INTO system (name, info, type, filename, status, throttle, bootstrap) VALUES ('dhtml_menu', 'a:9:{s:4:\"name\";s:10:\"DHTML Menu\";s:11:\"description\";s:49:\"Opens menus dynamically to reduce page refreshes.\";s:4:\"core\";s:3:\"6.x\";s:7:\"version\";s:7:\"6.x-3.5\";s:7:\"project\";s:10:\"dhtml_menu\";s:9:\"datestamp\";s:10:\"1244161838\";s:12:\"dependencies\";a:0:{}s:10:\"dependents\";a:0:{}s:3:\"php\";s:5:\"4.3.5\";}', 'module', 'sites/all/modules/dhtml_menu/dhtml_menu.module', 0, 0, 0) in C:\wamp\www\drupal-6.9\includes\module.inc on line 147.

my sites theme is colourise for all user

and aurora for admin....

how could i get ride of this warning,lease help....if it can harm my site?

thanks in advance