Windows Server 2025 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, including Virtualization Based Security and Credential Guard. Systems with UEFI that are operating in "Legacy BIOS" mode will not support these security features.

Devices that have UEFI firmware must run in UEFI mode.

Verify the system firmware is configured to run in UEFI mode, not Legacy BIOS.

Run "System Information".

Under "System Summary", if "BIOS Mode" does not display "UEFI", this is a finding.

Configure UEFI firmware to run in UEFI mode, not Legacy BIOS mode.