while ( $related = $db->get_row() ) {

Добавить выше:

$iz=1;
$buffer = "<table width="100%">";

3. Найти:

$buffer .= "<li><a href="" . $full_link . "">" . stripslashes( $related['title'] ) . "</a></li>";

Заменить на:

$iz++;
if($iz%2==0) {
    $z_s = "<tr>";
    $z_e = "";
} else {
    $z_s = "";
    $z_e = "</tr>";
}
$buffer .= $z_s."<td><a href="" . $full_link . "">" . stripslashes( $related['title'] ) . "</a></td>".$z_e;

4. Найти:

$tpl->set( '{related-news}', $buffer );

Добавить выше:

$buffer .="</table>";