Probá así:
Código PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>fixed</title>
<style>
#logo{ position:fixed; top:30px;}
</style>
<!--[if lt IE 7]>
<style>
#logo{
position:absolute;
top:0;
top: expression((ignorar = 30+document.documentElement.scrollTop+document.body.scrollTop) + 'px' );
}</style>
<![endif]-->
</head>
<body>
<img id="logo" src="http://static.forosdelweb.com/fdwtheme/logo-reflejo.png" /><br />
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</body>
</html>
Edito: Perdón David por el choque ;)