Mage/Adminhtml/controllers/Sales/OrderController.php

<admin>
        <routers>
            <adminhtml>
                <args>
                    <modules>
                        <mymodule_resetdownloads before="Mage_Adminhtml">Mymodule_Resetdownloads_Adminhtml</mymodule_resetdownloads>
                    </modules>
                </args>
            </adminhtml>
        </routers>
    </admin>

require_once (Mage::getModuleDir('controllers','Mage_Adminhtml').DS.'Sales/OrderController.php');
class Mymodule_Resetdownloads_Adminhtml_Sales_OrderController extends Mage_Adminhtml_Controller_Action
{

    public function resetAction() {

        $id = $this->getRequest()->getParam('id');
        $this->loadLayout();
        $this->renderLayout();
        echo $id;
    }


}