How to Delete all contents on USB drive including the protected hidden partition using windows 7 or 8 (I used this method to fix the size of usb drive on Fire TV)

Right click the my computer icon
Click manage
Disk management
Check the Disk name for your usb drive mine is Disc 1
Now open cmd as administrator (right click and run as administrator)
Type C:\Windows\
You should now see a list of the disks online.
Type select disk 1 or whatever your disk number is you want to delete.
Type list disk again just to make sure you have the right disk selected it should say *Disk 1 Online.
Type clear this will delete all partitions including hidden EFB partitions and everything else on the disk.

Exit CMD

Go back to manage disk drives and enable/format the usb drive.

If your Fire tv shows usb drive a 197mb then it is looking at the hidden partition on your usb drive follow the above instructions to fix this