My SP4 won't "see" or allow the Micro SD card to be added as a drive for File History. Yet, I've successfully used this card on two of the cheapie Win8 tablets (upgraded to Win10), and File History worked fine on both of them. I've reformatted the card to NTFS on the SP4, so left-over crud shouldn't be an issue. Why can't I use the Micro SD on the SP4 for File History. Seems absolutely stupid to have to plug in some USB flash drive for that purpose, when I've got a card installed in/on the unit.