The correct path of your new controller is :
app/code/community/Pinto/PartnerSystem/controllers/Adminhtml/Sales/Order/CreateController.php
(switch the folders controllers
and Adminhtml
).
This line from config:
<partnersystem before="Mage_Adminhtml">PartnerSystem_Adminhtml_Sales_Order_CreateController</partnersystem>
should be
<partnersystem before="Mage_Adminhtml">Pinto_PartnerSystem_Adminhtml</partnersystem>
and in your new controller file, before the class definitions add this
require_once 'Mage/Adminhtml/controllers/Sales/Order/CreateController.php'
[EDIT]
The new controller class name should be Pinto_PartnerSystem_Adminhtml_Sales_Order_CreateController
.