How to fix UNMOUNTABLE_BOOT_VOLUME error in Windows 11

by Alan Pfahler on March 5, 20262026-03-05T01:56:47+00:00

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Microsoft confirmed on February 2, 2026, that some PCs experienced startup problems after installing cumulative update KB5074109. The issue manifests as a blue screen, system freeze, and error code "UNMOUNTABLE_BOOT_VOLUME".

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Your device ran into a problem and needs to restart.
We'll restart for you.

Stop code: UNMOUNTABLE_BOOT_VOLUME

An easy way is to reinstall Windows 11.

Refer to this article for instructions on how to reinstall Windows 11. You can also use our product to reinstall Windows 11.