jomla 1.5 : Admin Menu Drop Down is not working

1) copy the /media folder in to the Administrator folder and edit .

2) Administrator/includes/application.php, line 118 which you should find is:
$document->addScript( JURI::root(true).'/includes/js/joomla.javascript.js');

3) change this to $document->
addScript( JURI::root(true).'/../includes/js/joomla.javascript.js');