This is done in the order.php class ...
The actual information being put into the orders_products table is done around 738-752:
Code:
$sql_data_array = array('orders_id' => $zf_insert_id,
'products_id' => zen_get_prid($this->products[$i]['id']),
'products_model' => $this->products[$i]['model'],
'products_name' => $this->products[$i]['name'],
'products_price' => $this->products[$i]['price'],
'final_price' => $this->products[$i]['final_price'],
'onetime_charges' => $this->products[$i]['onetime_charges'],
'products_tax' => $this->products[$i]['tax'],
'products_quantity' => $this->products[$i]['qty'],
'products_priced_by_attribute' => $this->products[$i]['products_priced_by_attribute'],
'product_is_free' => $this->products[$i]['product_is_free'],
'products_discount_type' => $this->products[$i]['products_discount_type'],
'products_discount_type_from' => $this->products[$i]['products_discount_type_from'],
'products_prid' => $this->products[$i]['id']);
zen_db_perform(TABLE_ORDERS_PRODUCTS, $sql_data_array);