<remove name="right"/>
<remove name="left"/>
<block type="checkout/onepage_payment_methods" name="root" output="toHtml" template="checkout/onepage/payment/methods.phtml">
   <action method="setMethodFormTemplate">
      <method>purchaseorder</method>
      <template>payment/form/purchaseorder.phtml</template>
   </action>
   <block type="core/template" name="checkout.onepage.payment.methods.scripts" as="scripts"/>
   <block type="core/template" name="checkout.onepage.payment.methods.additional" as="additional"/>
</block>
