WORKS FOR ANY VBULLETIN VERSION
Okay. Well here it is... put this into a file, and save it as registered.php .. then make an #include to put it on any .shtml page on your site.
Code:
<?php
require("admin/cnfg.php");
$dbclassname="admin/db_$dbservertype.php";
require($dbclassname);
$DB_site=new DB_Sql_vb;
$DB_site->appname="VBulletin";
$DB_site->appshortname="VBulletin (forum)";
$DB_site->database=$dbname;
$DB_site->server=$servername;
$DB_site->user=$dbusername;
$DB_site->password=$dbpassword;
$DB_site->connect();
$numbersmembers=$DB_site->query_first("SELECT COUNT(userid) AS users FROM user");
$numbermembers=$numbersmembers[users];
echo "$numbermembers";
?>
Upload this .php file in your VBulletin directory, so if your VBulletin directory is, blah.com/forums, upload into forums, so it would be blah.com/forums/registered.php.
Where you put the include, is where it will show the number of registered users on your board.
Enjoy.