Recommend to Create USBBoot on Win8 or 8.1

Step1 : Format usb to
FAT32Step2 : Copy file form ISO\WIM to USB
Step3 : Run Command Prompt as Administrator and type
BootSect /nt60 G: /force /mbr
[G = USB letter]
After create it will Dualboot USB [BIOS+UEFI Bootable]