Have you installed Backtrack on the USB following the official guides ?
I am unable to run backtrack5 on my old motherboard.
I got this new motherboard. I am unable to boot computer with USB. I have USB as first priory, dvd 2nd, and hard disk 3rd.
I have boot options correctly.
But just that when my computer start. It doesn't do any boot for USB, but it does boot for disc.