Alternatively you may want to place your code in the file:
wp-admin/edit-attachment-rows.php
after line 94:
place the following:
echo "<BR /><span class='$action'>URL: $post->guid</span>";
So it looks like this:
<td <?php echo $attributes ?>><strong><a href="<?php echo get_edit_post_link( $post->ID ); ?>" title="<?php echo attribute_escape(sprintf(__('Edit "%s"'), $att_title)); ?>"><?php echo $att_title; ?></a></strong><br />
<?php echo strtoupper(preg_replace('/^.*?\.(\w+)$/', '$1', get_attached_file($post->ID))); ?>
<p>
<?php
$actions = array();
if ( current_user_can('edit_post', $post->ID) )
$actions['edit'] = '<a href="' . get_edit_post_link($post->ID, true) . '">' . __('Edit') . '</a>';
if ( current_user_can('delete_post', $post->ID) )
$actions['delete'] = "<a class='submitdelete' href='" . wp_nonce_url("post.php?action=delete&post=$post->ID", 'delete-post_' . $post->ID) . "' onclick=\"if ( confirm('" . js_escape(sprintf( ('draft' == $post->post_status) ? __("You are about to delete this attachment '%s'\n 'Cancel' to stop, 'OK' to delete.") : __("You are about to delete this attachment '%s'\n 'Cancel' to stop, 'OK' to delete."), $post->post_title )) . "') ) { return true;}return false;\">" . __('Delete') . "</a>";
$actions['view'] = '<a href="' . get_permalink($post->ID) . '" title="' . attribute_escape(sprintf(__('View "%s"'), $title)) . '" rel="permalink">' . __('View') . '</a>';
$action_count = count($actions);
$i = 0;
echo '<div class="row-actions">';
foreach ( $actions as $action => $link ) {
++$i;
( $i == $action_count ) ? $sep = '' : $sep = ' | ';
echo "<span class='$action'>$link$sep</span>";
}
echo "<BR /><span class='$action'>URL: $post->guid</span>";
echo '</div>';
?></p></td>
This will show the URL underneath
'Edit | Delete | New'
on Roll over.