Make sure you've updated before the deadline.

This article describes how to enable Secure Boot to install Windows 11. How Do I Enable Secure Boot? The easiest way to enable Secure Boot is to do so through UEFI. It's typically listed as one of the ...

Microsoft has recently begun replacing expiring Secure Boot certificates on eligible Windows 11 systems running 24H2 and 25H2 ...

Microsoft is rolling out "Secure Boot Allowed Key Exchange Key (KEK) Update," which requires a system reboot to finish ...

Microsoft confirms systems without updated Secure Boot certificates will boot normally but lose some security protections.

Updated firmware trust chains strengthen rootkit protection and zero-trust infrastructure security.

In June 2025, Microsoft announced that, in June 2026, it would begin deprecating Secure Boot certificates of Windows systems ...

It sounds to me like claiming that all old Windows versions will be unbootable is an overstatement. Rather, it's most likely the case that you won't be able to boot old media when Secure Boot is ...