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.
XDA Developers on MSN

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

It's not just January's one.
Opinion

Microsoft Confirms Windows 11's January Update Is Bricking Some PCs

The most recent January Windows Update is broken on a number of PCs, but at least virtual machines don't seem to be impacted.
Guru3D

Windows 11 January security update can break boot on 24H2/25H2

A fresh wave of Windows 11 update trouble is making the rounds, and this one is about as disruptive as it gets: some PCs reportedly can’t boot after installing the latest January 2026 security update.

Microsoft issues second emergency patch for Windows this month - update your PC today

Microsoft issues second emergency patch for Windows this month - update your PC today ...