You trying to reformat it with Windows but Windows can't see it?
This needs Windows expertise presumably. It used to be done with fdisk but if nothing Windowsy can see it at all....
Were it me I'd plug it into something using Linux and then use Parted or Gparted, don't know if this will cope with the filesystem needed.
Use a live CD such as Ubuntu to turn a box into a Linux machine temporarily, without changing anything, if necessary.