header("Content-Type: multipart/mixed ");
$sid = mysql_real_escape_string($id);
$query = "SELECT name FROM files WHERE id='$sid';";
$res = mysql_query($query);
$name = mysql_result($res,0,0);
header('Content-type: application/force-download');
header('Content-Transfer-Encoding: Binary');
header('Content-length: '.filesize("f/$sid"));
header("Content-Disposition: attachment; filename=\"$name\"");
readfile("f/$sid");