Finding to be difficult to boot from USB on a VM, so :
tricks:
download plop boot manager
added it to CD as an ISO ( VM settings)
stop VM noot with ESC key
boot VM and choose CD drive to Boot
after booted to plop, choose USB
http://www.howtogeek.com/97923/how-to-boot-a-vmware-virtual-machine-from-a-usb-drive/
