account_interest_line/data/product_data.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
  <data noupdate="1">
    <record id="product_product_sale_order_interest" model="product.product">
      <field name="default_code">INTEREST</field>
      <field name="list_price">0.0</field>
      <field name="standard_price">0.0</field>
      <field name="type">service</field>
      <field name="name">INTEREST</field>
    </record>
  </data>
</openerp>