I am trying to figure out how to get my computer to boot from USB. Here's the issue. In BIOS I have put the USB on top, CD second and hard-drive third for boot order. But it will not boot from the USB. When I press F12 it doesn't show the USB at all, just the CD and hard-drive. When I am in the operating system (Ubuntu) and before that Windows 10, the USBs work fine. So I know that the USB connectors are connected inside my computer. I am completely baffled and befuddled. Please help. Thank you.