Can no longer be started Windows 11 patch paralyzes PCs - what you can do now
A Windows security update is supposed to close gaps and bring stability. But in January, Microsoft apparently achieved the opposite with a patch. In the meantime, some operating systems no longer even start up.
No time? blue News summarizes for you
- The January 2026 patch for Windows 11 can result in affected PCs no longer booting and displaying the error "UNMOUNTABLE_BOOT_VOLUME".
- The cause and exact solution are unclear. In some cases, users have to restore the system themselves and remove the update.
- The glitch is part of a series of update problems and reinforces doubts about the reliability of Microsoft's patch strategy.
What began as a routine patch day is increasingly developing into a structural problem for Microsoft. After a security update, Windows PCs were initially unable to shut down properly and in some cases are now unable to start. Instead, users only receive an error message. Windows Central initially reported on the dropouts, but Microsoft has now officially confirmed the problem.
Specifically, Windows hangs when booting up and displays the stop code "UNMOUNTABLE_BOOT_VOLUME". This error message indicates that Windows can no longer access the system partition correctly. Devices with Windows 11 versions 24H2 and 25H2 are currently affected.
It is not yet clear what the technical cause of the error is. Microsoft has not published any details. It is precisely this lack of transparency that increases the uncertainty. Without knowing the cause, it is difficult to assess which systems are at risk and whether further updates could have similar effects.
When the user becomes the system rescuer
The situation is particularly delicate for those affected. Anyone who can no longer start their system is denied access to classic troubleshooting. Microsoft only recommends "manual recovery measures" without actually carrying them out.
According to Windows Central, in many cases it boils down to manually repairing the system via the recovery environment and uninstalling the last installed update. This is a major hurdle for less tech-savvy users and a potentially costly scenario for companies with many workstations.
System restore when Windows is still starting
- Open the Control Panel, select Restore and then click Open System Restore.
- In the "Restore system files and settings" window, select the Next option.
- Select the item you want to use from the list. Tip: If the desired point in time does not appear, activate the Show more restore points checkbox.
- You can select Search for affected programs to see which apps may be missing after the process.
- Once you have found the correct point, select Next and then Finish. Windows will perform the restore and then restart automatically.
System restore when Windows no longer starts
- Switch on the PC. As soon as the Windows or manufacturer logo appears, press and hold the power button until the device switches off again.
- Repeat this process three times until the message "Automatic repair is being prepared" appears.
- On the blue screen, select in sequence: Advanced options → Troubleshooting → Advanced options → Restore system.
- Select your user account and enter your password.
- In the "Restore system files and settings" window, click Next.
- Select your restore point.
- Click Next and then Finish. Your system will be restored to the selected state and restarted.
Limited problem or structural risk?
It is currently difficult to reliably assess how widespread the startup problems actually are. The majority of users apparently do not report any difficulties. Microsoft itself refers to only a few reports. However, the fact that the company is publicly warning of a boot error after a security update underlines the explosive nature of the issue.
