Ok, after some discussion in question comments I suspect that the problem is in your install image. If you can't see GRUB menu then you are unable to enter bootloader on your USB drive. It might be several things causing your problem with common denominator - UEFI:
- You have written your install image incorrectly and UEFI is not recognizing it.
- You have written your install image correctly, but that image is not capable to run on UEFI - see discussion here.
Anyway 100% way to make Backtrack like most of current Linux distros to work on UEFI is to turn UEFI to legacy mode (BIOS), though you have to unninstall Windows 8 ;-)
I would not give lot of hopes to that because Backtrack 5 is based on Ubuntu 10.04 which is way too old - earliest Ubuntu supporting UEFI is 12.04.
I can recommend a few things that might help:
- Erase your usb flash drive and write Backtrack image to it again, but with UnetBootIn. There is an official tutorial for that.
- Do not try to install Backtrack 5 if don't know what GRUB is. You can install latest Ubuntu that can run on UEFI with SecureBoot (not sure it's easy) and enjoy all of the tools from Backtrack repositories.
Good Luck and have a lot of fun!