Dell, I'm angry at you. Your BIOS is worst I have seen in a while, confusing, inconsistent, and buggy, too. It seems to support legacy boot -- after you disable secure boot in one place and then enable legacy boot in another place, but if you read the fine print, you'll realize that it only works on usb media. It is hard to understand that as anything else than malice, so I'll say evil, too. Of course, you broke my boot. For others, avoid Dell optiplex 3060. Probably avoid Dell.