attenzione al browser che ti trovi davanti, devi mettere un controllo perchè c'è differenza tra IE e Firefox:

Codice PHP:
             $percorso='cartella dove si trova il file';
             
$name='nomefile';
              
// SE IL BROWSER È INTERNET EXPLORER
              
if(ereg("MSIE ([0-9].[0-9]{1,2})"$_SERVER["HTTP_USER_AGENT"]))
              {
                
header("Content-Type: application/octetstream");
                
header("Content-Disposition: inline; filename=$name");
                
header("Expires: 0");
                
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
                
header("Pragma: public");
              }
              else
              {
                
header("Content-Type: application/octet-stream");
                
header("Content-Disposition: attachment; filename=$name");
                
header("Expires: 0");
                
header("Pragma: no-cache");
              } 
              
$data=readfile($percorso.$name);
              echo 
$data