A WordPress Plugin for reattaching/unattaching media. Paste into functions.php, or put it in its own plugin file.

Reattach.php

add_filter("manage_upload_columns", 'upload_columns');
add_action("manage_media_custom_column", 'media_custom_columns', 0, 2);

function upload_columns($columns) {

	unset($columns['parent']);
	$columns['better_parent'] = "Parent";

	return $columns;

}
 function media_custom_columns($column_name, $id) {

	$post = get_post($id);

	if($column_name != 'better_parent')
		return;

		if ( $post->post_parent > 0 ) {
			if ( get_post($post->post_parent) ) {
				$title =_draft_or_post_title($post->post_parent);
			}
			?>
			<strong><a href="<?php echo get_edit_post_link( $post->post_parent ); ?>"><?php echo $title ?></a></strong>, <?php echo get_the_time(__('Y/m/d')); ?>
			<br />
			<a class="hide-if-no-js" onclick="findPosts.open('media[]','<?php echo $post->ID ?>');return false;" href="#the-list"><?php _e('Re-Attach'); ?></a>

			<?php
		} else {
			?>
			<?php _e('(Unattached)'); ?><br />
			<a class="hide-if-no-js" onclick="findPosts.open('media[]','<?php echo $post->ID ?>');return false;" href="#the-list"><?php _e('Attach'); ?></a>
			<?php
		}

}