how to boot from usb if my pc or laptop does not have the option?
-download zip
-extract it
-burn iso to cd

-boot from cd
-select USB
-press enter
-if you get message "Loading boot sector, waiting for any key to boot. N = continue search", 
press enter to continue booting from usb.

If it does not work, try pressing u, or "shift u", or "ctrl shift u".
as seen here,34.msg709.html