mount /dev/sdX /media/usbmount windows.iso /media/windowscp -rv /media/windows/* /media/usb/--boot-directory is the boot directory inside the iso.
sudo grub-install --target=i386-pc --boot-directory=/usbflash/boot/ /dev/sdXecho "If you see this, you have successfully booted from USB :)"
insmod ntfs
insmod search_fs_uuid
search --no-floppy --fs-uuid <UUID_from_step_2> --set root
ntldr /bootmgr
boot