A few Windows 11 users have been affected by a bug from the latest Windows 11 security update, which resulted in their PCs refusing to turn on. According to an AskWoody forum post, there were reports that some devices encountered an “UNMOUNTABLE_BOOT_VOLUME” error after installing the January 2026 Windows security update. The affected computers came up with a black screen and a message that says “Your device ran into a problem and needs a restart. You can restart.”\
This isn’t the first issue that came out of Microsoft’s latest Windows security update, with some PCs refusing to shut down or hibernate, and another bug resulting in Cloud-based apps, like Outlook, OneDrive, and Dropbox, not working, as reported by Windows Central. The company has since released emergency updates to address these problems, but it seems that there is no fix for the unbootable error just yet. This is also the most catastrophic error yet, and the only workaround for this is to enter the Windows Recovery Environment and uninstall the latest security patch.
