The regular way of booting into software and operating systems is called “Legacy Boot” and must sometimes be explicitly enabled/allowed in the BIOS settings. Legacy boot mode does not normally support partitions greater than 2TB in size, and can cause data loss or other problems if you try to use it normally.

What happens if I disable legacy support?

New Member. In my former system disabling legacy support meant the bios could no longer use USB, so you could not boot from a usb drive. Just keep it in mind for the future, you may have to turn it back on to use usb at boot.

Is it okay to use legacy?

It won't cause any damage. Legacy mode (a.k.a. BIOS mode, CSM boot) matters only when the operating system boots. Once it boots, it doesn't matter anymore. If everything works as expected and you're happy with it, legacy mode is fine.