Strange roblems with sessions

what it is meant to do:
take a querystring set it to a session variable (outputs error if neither
querystring nor sesison exist) then reloads the page (to remove the
querystring)
what it (appears) to do:
it sets the querysting to the session, reloads the page and outputs an error
saying it doesn't have the session variable
if you reload the page with a querystring back in and it works as it is
meant to
<------ the code in question -------->
<?
session_start();
if(!isset($_SESSION['HID']) && !isset($_SERVER['QUERY_STRING']))
die("There was an error registering your product please call techinal
support at (111)-111-1111");
else if(!isset($_SESSION['HID']) && isset($_SERVER['QUERY_STRING']))
{
$_SESSION['HID'] = $_SERVER['QUERY_STRING'];
header("Location: http://localhost/PHP/registration_form.php";);
}
?>
<--------------------------------->
I have attached the actual files if that would be of more help,
Thanks in advance for any help,
~Logan