When you open a Microsoft Office InfoPath 2003 form template in Microsoft Office InfoPath 2007, the form template remains compatible with InfoPath 2003 and will work in both versions of InfoPath. If you want to add Office InfoPath 2007-only features to your form template, such as Information Rights Management (IRM), you must explicitly upgrade that form template to Office InfoPath 2007 format, as described in the following procedure.
Note: After you upgrade a form template to Office InfoPath 2007, users can no longer open it in InfoPath 2003.
Open your InfoPath 2003 form template in Office InfoPath 2007 design mode.
On the File menu, click Save As.
By default, InfoPath 2003 Form Template is selected in the Save as type box, which means that your form template is currently compatible with both InfoPath 2003 and Office InfoPath 2007.
To upgrade the form template to Office InfoPath 2007 format, select InfoPath Form Template in the Save as type box, and then click Save.