[Zope] Installed Products

Does the list of installed products shown in the Control Panel actually get verified when Zope starts up or is it just a static list which gets updated when new products are added? AIUI the products shown should correspond to directories in the Products directory under Zope, but whilst the Control Panel shows ArchExample was installed, no such directory exists. Can anyone explain what is going on? Can I get Zope to refresh the list of products? -- John