Orders – How to Identify Guest vs Registered Customer Orders

Let's say that you have the order id 10000015: So

$orderId = '10000015';
$order = Mage::getModel('sales/order')->loadByIncrementId($orderId);
$billingAddress = $order->getBillingAddress();
$shippingAddress = $order->getShippingAddress();

For guest , magento have it customer_id as null.So you need to sales model by guest email address and magento set a flagcustomer_is_guest =1whenever customer will checkout as guest.

Note: Magento also save Customer email address to sales model table whenever loggin customers are checkout ,so on this case customer_is_guest =1 is importand

    $orderCollection = Mage::getModel("sales/order")->getCollection()
    ->addFieldToFilter('customer_email',$Customeremail)
    ->addFieldToFilter('customer_is_guest',1) ->addFieldToSelect('*');
foreach( $orderCollection  as $eachorder){
//var_dump($eachOrder)
}