To add a new page to a theme in CS2007, Add the page to SiteUrls_Override.config The SiteUrls.config file defines all of the rewritten URLs within Community Server. The SiteUrls_Override.config file within the root of the Community Server installation
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Read the complete post at http://getben.com/archive/2007/05/14/adding-new-themed-pages-in-cs2007.aspx