Legacy Boot refers to booting using pre-UEFI BIOS firmware. Booting some operating systems may require allowing Legacy Boot in addition to disabling Secure Boot. To do this, navigate to Startup and change the UEFI/Legacy Boot to allow legacy booting; you can enable UEFI, Legacy or both, and choose a priority order in the latter case. The CSM, or Compatibility Support Module, must also be enabled so the firmware may boot from a boot sector. Our examples use UEFI.