What version of Windows are you running and what KB were you attempting to install?

Could you try again, and immediately after the error comes up, open up the following log files and see what it happens to say as to why it failed.

WindowsUpdate.log
CBS.log

It will give clues as to the issue but might require a bit of interpretation - you could post the last 10 lines of both files here, shouldn't contain anything sensitive.

You could also try running this command which is a bit more aggressive than sfc /scannow

DISM /Online /Cleanup-Image /RestoreHealth

Thanks for the suggestions, and thanks for all the posts on this thread.

I entered the sfc and dism commands, and they both ran successfully. I then downloaded the installer and KB5066189. By running the installer, the problem became immediately apparent: Microsoft had decided that, although capable of running Win11 for a while, my laptop's processor was not strong enough to run later versions!

I think I may migrate to Linux!!

In reply to a post by Wagstaff:

By running the installer, the problem became immediately apparent: Microsoft had decided that, although capable of running Win11 for a while, my laptop's processor was not strong enough to run later versions!

Your CPU must have last been sold in 2018 or earlier then? What is it?

I think I may migrate to Linux!!

Ubuntu and Mint are both popular, but depends what you do with your computer. In my case I use more than the web and LibreOffice.

I'm running a refurbished ThinkPad, with an Intel i5 - 6200U processor, which is capable of running almost any modern Linux distribution - according to AI!!

I just don't understand why Microsoft should decide that the processor, which is happily carrying out the instructions of the Win11 software, is suddenly unable to fulfil the tasks in later updates.

In reply to a post by Wagstaff:

I just don't understand why Microsoft should decide that the processor, which is happily carrying out the instructions of the Win11 software, is suddenly unable to fulfil the tasks in later updates.

Chip manufacturers introduce new features. Linux does not predicate on those features rather it predicates on backward compatibility within the chips. Windows takes up the features, which obsoletes older processors. Computer manufacturers and chip manufacturers are rewarded for going with windows because it flushes older, but serviceable hardware to landfill. Microsoft benefits by selling more operating system licences,

In reply to a post by Wagstaff:

I'm running a refurbished ThinkPad, with an Intel i5 - 6200U processor, which is capable of running almost any modern Linux distribution - according to AI!!

A 2016 era CPU. I've got a 2014 era CPU at home that is now running Mint. I now have a 12th Gen that has Windows in a VM.

I just don't understand why Microsoft should decide that the processor, which is happily carrying out the instructions of the Win11 software, is suddenly unable to fulfil the tasks in later updates.

Microsoft and Apple and others have decided the 8th gen has hardware security support that they want to rely on. Some enterprise distributions of Linux have stopped support for CPUs before this. I don't mind as 8th gen is now 8 years old, so I upgraded for newer RAM and NVMe support; its less of an issue than it was in 2022.

In reply to a post by jchamier:

I've got a 2014 era CPU at home that is now running Mint. I now have a 12th Gen that has Windows in a VM.

How well do WVMs run inside Linux?

In reply to a post by Wagstaff:

In reply to a post by jchamier:

I've got a 2014 era CPU at home that is now running Mint. I now have a 12th Gen that has Windows in a VM.

How well do WVMs run inside Linux?

I am running several VMs one is Win 11 inside Solus Plasma with virtual box. 4 CPU and 8GB allocated with a 9th gen i5 and it runs well. Often use it for things Linux has trouble with.

Quite well, you can now use VMWare Workstation for free as a home user, it has Windows and Linux versions. Or you can use a Linux hypervisor, lots to choose from.