If you've modified your form.xsd file and want to get those nodes into your template and sample data files in Infopath 2003...best way i've found is:
1. Only works on mandatory items (so you can always make sure the item is mandatory (usage min 1) first and change it back afterwards)
2. Open your form
3. Choose any control that's already bound that has a default value e.g. a text box
4. Choose Properties
5. Alter the default value, and change it back.
The files should be regenerated. Stops you getting the unbound control errors and having to manually re-create the nodes.