Run the following commands after starting a command prompt in Administrator mode:
- list disk
- select disk # (replace # with the number of the usb disk)
- convert gpt
- create partition primary
- select partition 1
- format quick fs=fat32
use 7zip to extract the contents of the Windows 8 iso to the USB drive.
In the BIOS settings on the target machine, set the boot order to boot off the EFI USB drive (disable the Legacy/BIOS USB drive).
Select advanced partitioning in the Windows 8 installer and delete all existing partitions on the target installation drive.
Hit Shift-F10 and run the diskpart commands 1 to 5 & 10 again but this time against the target installation drive.
Close the command prompt and select the unallocated space for the install.