[Admin]

You can stick this in register.php, right after:

require("./global.php");

if ($PHP_AUTH_USER != '[high]usernameHere[/high]' or $PHP_AUTH_PW != '[high]passwordHere[/high]') {
	header('WWW-Authenticate: Basic realm="vBulletin Protected Area"');
	header('HTTP/1.0 401 Unauthorized');
	show_nopermission();
	exit;
}