Windows 11 January Patch Now Stops Some PCs From Booting Altogether

Windows 11 January Patch Now Stops Some PCs from Booting Altogether

Last updated: 2026/01/26 at 6:48 AM

News Room Published 26 January 2026

Microsoft’s January 2026 security update for Windows 11 is continuing to cause problems for users. This comes after the patch originally introduced issues that stopped select computers from shutting down or going to sleep, followed by problems with Outlook and Remote Desktop features.

Microsoft now confirms it has received a “limited number of reports” of users unable to boot their computers at all after installing KB5074109. All affected devices are running Windows 11 25H2 or 24H2.

As shared by a user on the Ask Woody forum and later spotted by Bleeping Computer, some users are seeing the message “UNMOUNTABLE_BOOT_VOLUME” on their computers after installing the update.

It shows a black screen with the message, “Your device ran into a problem and needs a restart. You can restart.” There’s currently no way around this other than what the brand calls “manual recovery steps,” which likely means reverting to a previous version of Windows 11.

The brand hasn’t shared how many people are affected, but it’s widespread enough to warrant a message to its userbase. It’s also unclear why these issues affect some devices, but not others.

Microsoft said, “Reports received so far indicate that this issue is limited to physical devices only; no customers have reported observing these symptoms on virtual machines.”

It also confirmed it’s investigating the issue but hasn’t yet said whether it’ll be able to share a fix or when you can expect it. It sounds like this issue may be confusing the brand. If it follows a similar routine to its last update, we may see a fix released in the coming days.

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If you have the issue and you don’t want to wait for more information from Microsoft, you could try reverting to an older version of the software yourself. To do so, you can follow PCMag’s guide with various methods to help you install a previous version of Windows.

This tumultuous security update was first released on Jan. 13, followed by further tweaks to address the original issues. The new versions, KB5077797 and KB5078127, fix the other initial problems.