You could try downloading the ISO using the tool instead of letting it make the USB, and use Rufus to make the USB instead, that way you don't have to download it multiple times and have it fail: http://www.techverse.net/how-to-create-bootable-usb-flash-drive-install-windows-8-1/
I assume PC can see the USB, it just has issues copying to it. Have you tried another USB?