2
           
            
                
     
    
    I'm basing this off 1.63 as I've not put 1.67 into use yet. However:
archive.php line 114:
 $result = $xoopsDB->query('SELECT published FROM '.$xoopsDB->prefix('stories').' WHERE (published>0 AND published<='.time().') AND (expired = 0 OR expired <= '.time().') ORDER BY published DESC');  
remove the expired stuff from the where clause so that it looks like:
 $result = $xoopsDB->query('SELECT published FROM '.$xoopsDB->prefix('stories').' WHERE (published>0 AND published<='.time().') ORDER BY published DESC');  
You will also have to change the article page to allow expired articles to be viewed:
article.php lines 144-158:
 // Expired 
if ( $article->expired() != 0 && $article->expired() < time() ) { 
    redirect_header(XOOPS_URL.'/modules/news/index.php', 2, _NW_NOSTORY); 
    exit(); 
}  
You can likely just comment all that code out and it should work.
YMMV.