To change existing items so that they display using a published custom message form, you need to change the value of the MessageClass property on each item so that it points to the published form's class, e.g. IPM.Contact.MyForm. The page at http://www.outlookcode.com/d/newdefaultform.htm has links to scripts and tools to do this.
--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers