I set up an external hard drive to boot using this videos instructions: https://www.youtube.com/watch?v=gsAzRGMimgQ
When I try to boot to the hard drive on my old computer it will start up and I will see the startup screen and it will go black as if it were about to boot, but instead to just restarts and does the same thing again and again. I tried another computer and it simply booted to a black screen. Both computers recognize my hard drive as a bootable device but both fail to boot properly. What do I do?
