You do not want to use Attachment-Pages in your WordPress page? Or maybe you installed a gallery Plugin and want to transform all your Attachment URLs into File-URLs now? The following script will do this for you. Just make sure, that all relevant content blocks of your database run through this script.

function cis_file_links($content) {
 
	$content = stripslashes($content);
 	
	$matches = array();
	$attachment_urls = preg_match_all("/href=\"([-A-Z0-9+&@#\/%?=~_|!:,.;]*)\?attachment_id=([0-9]*)\"/siU",$content,$matches);
 
	$urls = array();
	foreach($matches[2] as $attachment) {
		array_push($urls,wp_get_attachment_url($attachment));
	}
 
	// something went wrong with geting the attachments
	if(count($matches[2])!=count($urls)) {
		return $content;
	}
 
	for($i=0;$i
If you want to apply this script to every displayed content, for example, without changing any contents of your database, add this filter to your functions.php:
add_filter('the_content','cis_file_links');

Improvement ideas are welcome.