i had some problems before with the microsd:when i put the sdcard i ALWAYS did click in storage (in win10 my tablet is dual os) to make the sd card the storage by default although id didn’t work(the tablet always made C to default storage) it created some folders like windows apps,admin etc, i think the problem was that so i formated my sd card(fat32) and i did not clicked that option and it works fine when i extract the microsd (always use extract with safety) and now i can put stuff via my pc and when i put it now again in the tablet works,nothing is corrupted or access denied etc i hope that help you
EDIT: i forgot to tell you that if your tablet is in windows mode and you connect the tablet with an usb to the pc will not work (i wanted the same as you) ,only in android mode,the reason here (sorry it is in spanish,try google translate or something) http://answers.microsoft.com/es-es/windows/forum/windows_8-networking/como-hago-para-conectar-mi-tablet-win-8-a-un/aad59c70-74f6-4560-aa4d-b06b08940f65?auth=1