I have just bought a new 64gb sd card for my Galaxy 10.1 tablet, and it does not show when I usb it to my computer - I want to put some .avi files on it, so do I need to format this card for it to use, I notice with I inserted the card it gave me "preparing sd card" message - so does anyone have any advice? I have tried to "mount" the sd card but nothing seems to happen