Getting a Prohibited Symbol when trying to boot from USB 3.0

Hello everyone, I have recently installed Mac OS X 10.10 on my HP Pavilion DV6700 series laptop, and I am trying to install Mac OS X 10.11 El Capitan. I currently only have a USB 3.0 drive, but before I had a USB 2.0 drive which I lost a long time ago. Anyway, when booting with the USB 3.0 with Unibeast installed, I get a prohibited symbol and have found no solution to this. I was hoping anyone could help, or if I would have to buy myself a new USB 2.0 drive just to install the updated OS. Hopefully someone can help!

submitted by /u/Pelicanfuture
[link] [comments]