I'm currently working on upgrading a Sharepoint 2003 installation to a Sharepoint 2007 installation. I am using a custom site definition in 2003 and would like to map that to the out of the box "Team Site" definition in 2007. Assume my custom site definition is called CustomSiteDef. I have created an upgrade definition file called CustomSiteDefUpgrade.xml. When I perform the upgrade it complains about not finding onet.xml. The upgrade is looking for a site definition on the 2007 installation of the same name and cannot find it. I never created this site definition in 2007 because I was planning to map it to the out of the box Team Site definition. The question is how do I map the custom site definition in 2003 to an out of the box definition in 2007?