Windows 11 25H2/24H2 PCs at risk of Blue Screen of Death instead of booting after KB5074109 from January 13

Windows 11 25H2/24H2 PCs at Risk of Blue Screen of Death Instead of Booting After January 13 KB5074109

Microsoft is truly going through a rough patch with the latest Windows 11 updates: after installing the January 13 KB5074109 update, some PCs (version 25H2/24H2, build 26200.7623) have stopped booting. Instead, users are getting a Blue Screen of Death with the stop code UNMOUNTABLE_BOOT_VOLUME, which in other situations could indicate system corruption, a BIOS/bootloader malfunction, or a hardware failure, often related to the disk.

The support document is only available to Microsoft 365 business account holders, so regular users are probably safe: "Microsoft has received a limited number of reports of an issue causing devices to fail to boot."

The scale of the issue is unknown, but it appears that only certain physical machines are affected; virtual machines are fine. The mandatory security update KB5074109 had already caused a number of problems earlier, which have now been fixed. The company has not suggested rolling it back to avoid further trouble; currently, specialists are collecting data and conducting an investigation.

You can check your Windows 11 build like this: "Settings" -> "System" -> "About".

Recall that in December 2025, the OS was updated in such a way that it started killing SSDs and HDDs, and in January 2026, devices running Windows 11 Enterprise and IoT version 23H2 with System Guard Secure Launch stopped shutting down.