PHP 5 has register_globals off. This is a good thing, as it prevents data forgery/manipulation through bogus GET/POST requests.
If you edit index.php to check $GET['goto'] instead of $goto everything should work as expected. Of course, you'll need to do the same for any other GET variables you use (so if you have a page number specified like "index.php?goto=january&page=2", you'd need to access $GET['page'] instead of $page). If you have any questions feel free to message me