Así es, en ambas lineas:
Código PHP:
if(isset($_SERVER['HTTP_USER_AGENT']) && strpos($_SERVER['HTTP_USER_AGENT'],'MSIE'))
{
header("Pragma: public");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
}
ob_clean();
header("Content-Encoding: ISO 8859-1");
header("Content-Type: application/vnd.ms-excel; charset='ISO 8859-1' ");
header("Content-Length: ".@filesize($fname));
header("Content-disposition: filename='$nombreR$b'");
$fh=fopen($fname, "rb");
fpassthru($fh);
unlink($fname);