Pages and Variables

I'm following the guide, to learn, and specifically in 'Pages and Variables'
I have a problem...
if i insert this on application / config / MY_fuel_modules.php :
$config['modules']['news'] = array('preview_path' => 'news/{slug}');
I have this error

An uncaught Exception was encountered

Type: RuntimeException

Message: Unable to locate the model you have specified: News_model

Filename: C:\xampp\htdocs\fuel\fuel\codeigniter\core\Loader.php

Line Number: 348

Backtrace:

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\core\Loader.php
Line: 237
Function: model

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\core\Loader.php
Line: 455
Function: model

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_modules.php
Line: 969
Function: module_model

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_modules.php
Line: 757
Function: model

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_posts.php
Line: 138
Function: info

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_posts.php
Line: 968
Function: module_config

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_pages.php
Line: 730
Function: find_module

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_pages.php
Line: 574
Function: assign_variables

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_pages.php
Line: 525
Function: initialize

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\libraries\Fuel_pages.php
Line: 65
Function: __construct

File: C:\xampp\htdocs\fuel\fuel\modules\fuel\controllers\Page_router.php
Line: 70
Function: create

File: C:\xampp\htdocs\fuel\index.php
Line: 364
Function: require_once