Windows 10 systems must have Unified Extensible Firmware Interface (UEFI) firmware and be configured to run in UEFI mode, not Legacy BIOS.
UEFI provides additional security features in comparison to legacy BIOS firmware, including Secure Boot. UEFI is required to support additional security features in Windows 10, including Virtualization Based Security and Credential Guard. Systems with UEFI that are operating in Legacy BIOS mode will not support these security features.
Some older systems may not have UEFI firmware. This is currently a CAT III; it will be raised in severity at a future date when broad support of Windows 10 hardware and firmware requirements are expected to be met. Devices that have UEFI firmware must run in UEFI mode.
Run "System Information".
Under "System Summary", if "BIOS Mode" does not display "UEFI", this is finding.
Fix Text (F-83781r1_fix)
Configure UEFI firmware to run in UEFI mode, not Legacy BIOS mode.