Install Microsoft’s emergency Windows patch now – what it fixes and why it was rushed out

ZDNET’s key takeaways

• Fixes a flaw that impacted the Windows reset and reinstall tools.
• The patch affects certain versions of Windows 10 and Windows 11.
• To install the patch, head to Windows Update under Settings.

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Microsoft has squashed a recent and annoying bug in Windows that caused the built-in reset and reinstall tools to fail if you tried to run them. Released on Tuesday, the new out-of-band emergency patch is designed for Windows 10 21H2 and 22H2, and Windows 11 23H2 and 22H2.

Also: Microsoft patches more than 100 Windows security flaws – update your PC now

Applying the patch should once again allow you to reset your PC or fix problems using Windows Update. Normally available, those two options can resolve an otherwise unresolvable system issue by forcing Windows to return to its original factory state, or by repairing key system files and components.

How to apply the patch

To apply the patch, just head to Settings, select Windows Update, and click the button to check for updates. Affected Windows 10 users will want to download and install the KB5066188 update, while Windows 11 users will find KB5066189 waiting for them.

From whence did this bug come? Blame it on Microsoft, for the glitch was introduced in the latest Patch Tuesday update.

Also: Your Windows 11 PC has a secret emergency shutdown feature – here’s how to use it

Microsoft’s monthly Windows updates usually try to fix the latest cavalcade of bugs. Last week’s August update patched more than 100 security flaws. But sometimes the update introduces bugs of its own. In this case, the latest monthly update somehow introduced a flaw that clobbered the reset and reinstall features.

Other options

I often use the reset feature with my Windows virtual machines when I want to bring the OS back to its original state. But this is also a handy option for dealing with issues that affect the performance or operation of Windows.

To try this in Windows 11, go to Settings, select System, choose Recovery, and then click the button to reset this PC. In Windows 10, head to Settings, select Update & Security, choose Recovery, and then click the Get Started button in the section to reset this PC.

When resetting your PC, you can choose to keep your personal files. However, your apps and customized settings are removed, so you’ll have to reinstall or recreate those. Since the reset brings Windows back to its original factory state, the process can resolve most system problems.

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The other option for reinstall attempts to fix major issues in Windows by repairing corrupted or incorrect system files, services, and settings. The advantage here is that your apps, documents, and settings are all preserved. I’ve used this a couple of times in the past, mostly with Windows VMs that were misbehaving, and it typically did the trick.

To try this option in Windows 11, go to Settings, select System, choose Recovery, and click the Reinstall now button. In Windows 10, the process is different. Here, go to Settings, select Update & Security, and choose Troubleshoot. Click the link for Additional troubleshooters, choose the one for Windows Update, and click the button for Windows Update troubleshooter.