when I try to boot from a bootable USB flash drive in windows 10, I throw this error and boot 10.
Answer 1, authority 100%
This is done in the BIOS (or UEFI) – usually in the “Boot” tab. There are items “Boot mode” and “Boot priority”. Some or both of them will have something related to UEFI. Should be changed to Normal (as a Legacy option) – Normal boot.