I've got an HP all-in-one that I need to reinstall windows 8.1 on. It was the native OS, but got corrupted when an update failed. In the BIOS, it allows me to set secure boot to "disabled", but when i attempt to enable the usb legacy option, it says I must disable secure boot first. It's already disabled, however. Any suggestions? No legacy sources can be enabled as a result of this error.