I have several problems with the zenithink zt 180, have a 8gb sandisk hc sdcard. In the settings i see sdcard and external-sd? What's the different? I can see that the external sdcard is visible and the sdcard not? When i tried to move a app to the sdcard i get the message: can't move, not enough space..? There is 8 GB, what the reason for that? On the market i get the message can't install: unknown reason 18? How to use the sdcard, does it be installed on a special way to be used or? thanks!