OK, I wasn't aware that only self developed programs will appear. After deploying and app I see the app GUID.
May be it makes sense to add a notification text in case no self-developed app is found on the device that only those will be visible (just for avoiding questions of WP7 beginners like me).
BTW. I noticed that the filebrowser is very sensitive regarding drag&drop operations. By just browsing the structure I copied directories several times. It happens if you click very fast through the list.