Cannot Boot into Windows after installing KB4100347 Intel CPU Update

Intel recently announced that they have completed their validations and started to release microcode for recent CPU platforms related to Spectre Variant 2 (CVE 2017-5715 [“Branch Target Injection”]). The Windows Update KB4100347 includes microcode updates from Intel.

Right after installing the update KB4100347 via Windows Update channel or the Microsoft Update Catalog, many users faced a problem where the system became unbootable, especially Xeon workstations. Although not necessary, some users wiped their drive, formatted it and installed Windows 10 from scratch to come out of this problem.

But there is no need to clean install Windows 10. This post explains how to make your Windows 10 computer bootable again by undoing/uninstalling KB4100347 offline via Windows Recovery Environment.

[Solution] Cannot boot into Windows after installing KB4100347

To fix the unbootable Windows 10 computer, uninstall KB4100347 package via Windows Recovery Environment.

Remove KB4100347 to fix your unbootable computer

1. Boot into Windows RE (press F9 before Windows starts). If Windows doesn’t start, then boot the system using the installation media or Recovery drive to access the Recovery Environment. In the Windows setup page that appears when booting using the Windows installation media, click Next and click Repair your computer. For more information, see how to boot into Windows RE.
2. Choose Advanced Options, and click on the Command Prompt option.
3. Next, find out now which drive-letter has been assigned for the Windows partition (when seen from WinRE). To do so, run the command diskpart
4. Then type list disk. Select the one which matches your Operating System drive.
5. Type list volumes. It’ll throw out a list. The biggest one should be Windows. Two small ones of around 500MB should be there, ignore those.
6. Close diskpart by typing exit
7. Now type dism /image:<driveletter here> /get-packages. This should result in a list of packages. Find KB4100347. It’s name is quite long, but you can copy it by selecting it and right clicking. It might appear like as below:

   Package_for_KB4100347~31bf3856ad364e35~amd64~~10.0.2.3

8. Now type dism /image:<driveletter here> /remove-package /PackageName:<the_long_package_name_here>
9. Now type dism /image:<driveletter here> /cleanup-image /revertpendingactions as to undo the damage done.

Credits to redittor a_false_vacuum for the quick fix above. See Reddit thread KB4100347 rendering systems unbootable for details.

Hope you were able to uninstall KB4100347 offline and now able to boot Windows successfully.

Further, to prevent the KB4100347 update from being reinstalled automatically, you can use the WUShowHide diagnostic .cab utility discussed in article Prevent Windows Update from Installing Certain Updates & Drivers and How to Defer a Windows 10 Update.

Or if you can take a small risk, install the latest BIOS update for your motherboard and then retry installing KB4100347. If the same problem happens even after BIOS update, you can follow the steps in this article to undo the update, again.