This Windows 10 update fail is the most serious yet – here’s what you need to do

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Windows 10 is suffering yet more problems thanks to a faulty update – and this one could be its most serious one yet, with users reporting Blue Screen of Death errors and deleted files after installing Windows 10 KB4549951.

Windows 10 KB4549951 was released by Microsoft on April 14, and was supposed to introduce a number of security fixes. However, as we reported earlier, the KB4549951 also introduced some serious issues, including the dreaded Blue Screen of Death.

However, since our initial report, its emerged that the problems introduced with the new update are far more serious than we first thought, as users are reporting that their personal files are moved or deleted after installing the update.

Deleted files

One user contacted Windows Latest to report that: “This update is a disaster. It deleted my files, pictures, documents saved in system drive and as well as my apps which I downloaded from Windows Store.”

Now, while encountering Blue Screen of Death problems, where your PC crashes and has to restart, is worrying, the fact that some people are now reporting that their files are deleted is seriously concerning.

Especially files in the Pictures and Documents folders. For many people these folders contain important and irreplaceable files, so having them deleted (or moved to another folder, which is sometimes happening) can cause a lot of stress and anxiety.

As Windows Latest reports, quite a few users have been complaining about this. “Data lost after upgrading [to] KB4549951. All files in Documents more than 1 week old are deleted without notification or moving to the Recycle Bin. No restore available, no help, no live chat, no nothing,” says one user who has experienced the issue.

A previous Windows 10 update caused similar issues, and this was discovered to be because it was creating a temporary user profile when Windows 10 boots, and removing some files and icons, while also resetting some settings to their defaults.

That problem was eventually fixed by Microsoft, so lets hope the company (which has yet to acknowledge this current round of problems) fixes this issue soon. We’ve reached out to Microsoft for comment.

Yet more issues

However, if the file deletion bug wasn’t bad enough, Windows 10 KB4549951 brings even more issues for some users.

We’ve already mentioned the Blue Screen of Death problems, and since originally reporting on those issues a few days ago, more users have taken to the internet to complain.

It now appears that the most common Blue Screen of Death error messages are:

  • Portcls.sys

While some people get BSOD every so often, requiring a PC reboot, others are getting a loop of BSOD errors, where the PC cannot boot without crashing instantly. This effectively makes the PC unusable.

There have also been reports that the update is causing some PCs to perform poorly after installation.

All-in-all, then, this is a bit of a nightmare update. Thankfully, there is a fix.

How to fix it

For the moment, the only reliable way to fix the issues introduced with Windows 10 KB4549951 is to uninstall the update. However, we should note that because this update introduces important security fixes, you should only uninstall it if you’re experiencing problems.

If you’ve installed the update and are having issues, follow the steps below to uninstall it:

Open the Settings app (the cog icon in the Start menu) click 'Update & security' and then click on 'Windows Update' in the left-hand menu

Next, click 'View update history'. Click 'Uninstall updates', find KB4549951 in the list of updates, select it, then click to uninstall.

Matt Hanson
Managing Editor, Core Tech

Matt is TechRadar's Managing Editor for Core Tech, looking after computing and mobile technology. Having written for a number of publications such as PC Plus, PC Format, T3 and Linux Format, there's no aspect of technology that Matt isn't passionate about, especially computing and PC gaming. He’s personally reviewed and used most of the laptops in our best laptops guide - and since joining TechRadar in 2014, he's reviewed over 250 laptops and computing accessories personally.