I am trying to transfer email addresses from a 2009 ASUS laptop (running the Windows 10 update to the original Windows 7 O/S) to another computer. I have the latest version of Thunderbird 5.9.1 on both computers. When I try to export one of my address books on the ASUS Windows 10 computer to a USB stick using the Export function, I get the message "There are no more files" and the location on the USB stick is empty. When I try to export an address book from the other computer using the exact same steps, it is successful, so there is nothing wrong with the steps I am using: Insert USB stick and create new file. Open Thunderbird Address Book, highlight the address book to be transferred and click Tools > Export. Select the USB stick and new file on the left side. Click "Save". I can easily save other files to the USB stick outside of Thunderbird.