You cannot switch from Legacy BIOS mode to UEFI BIOS mode until ... created PlatformAoAcOverride value. It should show 0 in its Value Data. If not, enter 0 and click OK. Restart your computer ...

Intel is working on a plan to remove so-called "last-mile" barriers to killing off legacy BIOS by requiring UEFI Class 3, which doesn't expose legacy BIOS interfaces. BIOS is the firmware that ...