how to reset the windows authentication

I made an intranet website by php, webserver IIS on windows 2000.
To manage users I used the windows authentication.
Now I have to create logout.php that has to destroy sessions and windows
authentication too,
to allow the login to another user from the same pc (for example).
I can destroy sessions variables by:
session_start();
$_SESSION = array();
session_destroy();

but how can I destroy or reset the windows authentication?
My problem is that I'm not able to display the window with user name,
password
and domain to change the window user. :-(