I've copied backtrack iso to flash drive using unetbootin tool, and set in BIOS "Removable device" as first boot choice, but doesn't boot from flash.
Tried R1 and R5 distributives.
Flash has this files in root directory:

.disk
casper
isolinux
preseed
ubninit
ubnkern
ubuntu
menu.c32
syslinux.cfg
README.diskdefines
ldlinux.sys
md5sum.txt
ubnfilel.txt
ubnpathl.txt