在xp系统下点击 下载附件 后网页自动关闭了

[lvfeng]

代码如下
<?php
require("../include/setting.php");

$dfname=$office_upload.$file;

header("Content-type: application/octetstream");
header("Content-Disposition: attachment; filename=$file");
header("Accept-Ranges: bytes");
header("Content-Length: ".filesize($dfname));
header("Pragma: no-cache");
header("Expires: 0");
@readfile($dfname);
exit();
?>

win200下很正常，谁知道说一下啊