Microsoft investigates Windows 11 boot failures after January updates

Microsoft is investigating reports that some Windows 11 devices are failing to boot with "UNMOUNTABLE_BOOT_VOLUME" errors ...
Windows Report

KB5074109 Update Causes Boot Failures on Windows 11 Devices

Windows 11 January 2026 updates may cause boot failures on some PCs. Microsoft is investigating issues linked to KB5074109.
Windows Latest

Microsoft confirms Windows 11 KB5074109 January update BSOD, boot issues on some PCs ...

Windows 11 KB5074109 (January 2026 Update) is causing major issues on some PCs, and Microsoft has more details to share.

Windows Updates: New Boot Certificates, Error Fixes, and New Problems

Microsoft released unplanned updates over the weekend. They correct errors in the January patches and bring new boot certificates.
Tom's Hardware on MSN

Some PCs can't boot after latest Windows 11 security update, no fix in sight — mostly ...

A Windows security update bug has prevented some Windows 11 24H2 and 25H2 users from booting into their PCs, requiring them ...
PR TIMES

Windowsのエラー0xc000021aを修復する方法‐4DDiG Windows Boot Genius

Windowsのエラーで0xc00021aが表示されたら、どう解決すればいいか？Tenorshare社は2023年2月6日(月)にWindows Boot Genius V1.0.7をリリースしました。4DDiG Windows Boot Geniusを使用すると、Windowsのエラーを簡単に修正できます。 「0xc00021aというエラーが出るのはなぜなのか？
XDA Developers on MSN

Microsoft confirms that a stack of bad Windows updates is causing boot issues

It's not just January's one.
Daily Times

Microsoft probes windows 11 boot errors after update

Microsoft is investigating reports of serious boot failures affecting Windows 11 devices following the January 2026 security ...