Just for reference, includes/config.php should look like the following, for the first setting, according to Zachary.
Code:
// ****** DATABASE TYPE ******
// This is the type of the database server on which your vBulletin database will be located.
// Valid options are mysql and mysqli, for slave support add _slave. Try to use mysqli if you are using PHP 5 and MySQL 4.1+
// for slave options just append _slave to your preferred database type.
$config['Database']['dbtype'] = 'mysqli';