Since ArcGIS 10 during the Visual Studio build an additional target with the execution of a program named esriRegasm is called. Amongst other things this program adds the COM-categories in the registry. If you need to call this program outside a build at an own cmd-prompt you could often see some strange errors. Having the right permissions First at all you need administration permissions. This is for the registry-entries. You could open an admin-cmd like: Win + R runas /user:<AdminUser> cmd ......