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

Microsoft is aware of an alleged issue that leaves PCs unable to boot and requires manual recovery after Windows 11 January ...

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

Microsoft has linked recent reports of Windows 11 boot failures after installing the January 2026 updates to previously failed attempts to install the December 2025 security update, which left systems ...