Explanation
Internet Explorer 5 and later for Windows allow you to hack using a conditional comment. In the case of processing in Win+IE5 and above, put contents which you like to show between <!--[if gte IE 5.0]> and <![endif]-->. As other browsers treat them as a standard comment, they won't be displayed.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=shift_jis">
<title>Sample</title>
</head>
<body>
<h1>Sample</h1>
<p>
If your browser is Win+IE5 and above, a text will be shown in the line below.<br>
<!--[if gte IE 5.0]>
It's Windows + IE5 and above.
<![endif]-->
</p>
</body>
</html>