wget http://download.gna.org/grub4dos/grub4dos-0.4.4.zip; unzip grub4dos-0.4.4.zip
mkdosfs -F32 -I /dev/sdb1 #format usb FAT32
./grub4dos-0.4.4/bootlace.com /dev/sdb #make usb bootable
mount /dev/sdb1 /mnt; cp grub4dos-0.4.4/grldr YOUR_IMAGE.iso /mnt
mount /dev/sdb1 /mnt; cp grub4dos-0.4.4/grldr YOUR_IMAGE.iso /mnt
title bootable-usb
map (hd0,0)/disk.iso (hd32)
map --hook
chainloader (hd32)
boot
EOF
EOF
Reboot and select booting from USB.
BIG THANKS to http://www.thinkwiki.org/wiki/BIOS_Upgrade#Booting_from_a_USB_Flash_drive