根据上面的截图 ，我们发现支付部分的代码是

<div id="order-methods">
            <div id="order-billing_method" class="box-left payments"><?php echo $this->getChildHtml('billing_method') ?></div>
           。。。。。。
        </div>

在这个文件：D:\www\lollicupStore2\app\design\adminhtml\default\default\layout\amasty\amstcred\amstcred.xml 对原来的代码进行了重写

 <adminhtml_sales_order_create_index>
        <reference name="billing_method">
            <block type="amstcred/adminhtml_sales_order_create_payment" template="amasty/amstcred/sales/order/create/payment.phtml" name="reward_points" before="-" />
        </reference>
    </adminhtml_sales_order_create_index>

    <adminhtml_sales_order_create_load_block_billing_method>
        <reference name="billing_method">
            <block type="amstcred/adminhtml_sales_order_create_payment" template="amasty/amstcred/sales/order/create/payment.phtml" name="reward_points" before="-" />
        </reference>
    </adminhtml_sales_order_create_load_block_billing_method>

    <adminhtml_sales_order_create_load_block_data>
        <reference name="billing_method">
            <block type="amstcred/adminhtml_sales_order_create_payment" template="amasty/amstcred/sales/order/create/payment.phtml" name="reward_points" before="-" />
        </reference>
    </adminhtml_sales_order_create_load_block_data>

我们需要找到重写着部分代码的block以及模板文件 。

amstcred/adminhtml_sales_order_create_payment
amasty/amstcred/sales/order/create/payment.phtml

block： amstcred/adminhtml_sales_order_create_payment 其实是文件

D:\www\lollicupStore2\app\code\local\Amasty\StoreCredit\Block\Adminhtml\Sales\Order\Create\Payment.php

至于原因，仔细看config.xml文件 D:\www\lollicupStore2\app\code\local\Amasty\StoreCredit\etc\config.xml