Local group missing after  windows 11 update.

Hello, I'm Greg, here to help you with this.

1) Try these fixes for Windows 11 Local User Group missing after Update:

https://www.makeuseof.com/windows-home-edition-...

https://droidrant.com/why-are-local-users-and-g...

https://www.reddit.com/r/Windows10/comments/lrj...

2) Since you know when this happened, See if you can System Restore to a point before this started. System Restore is a time machine that takes you back to a point where Windows was working correctly: https://beebom.com/how-system-restore-windows-11/

If the problem repeats then System Restore again or uninstall any Updates that were just installed in Settings > Windows Update > Update History, restart Windows and immediately block those Updates as shown here:
https://www.droidwin.com/how-to-stop-only-a-spe...

3) Go over Windows 11 with this Performance Checklist to make sure the install is set up correctly, optimized for best performance, and to find and fix problems:
https://answers.microsoft.com/en-us/windows/for...

4) If nothing else works then do a minor, non-destructive Repair Install which reinstalls Windows while saving your files, apps and most settings in place, brings it up to the latest version by the most stable method, takes about an hour and resolves most problems: https://www.elevenforum.com/t/repair-install-wi...

Let me know if you have any questions or I can help performing any of the above steps. If you'll post back detailed results it will help me determine what else needs to be tried.
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Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.

thanks!

Folder Windows.old was deleted by me and cannot be restored。

I tried to keep the data and reinstall the system, but the problem didn't work out.

According to your prompt, I downloaded lusrmgr.exe, but there was an obvious error when it ran:

now, how can i do ?

That's just the first steps. Please continue with all steps until one works. If nothing else does, then the simple in-place Repair Install will always work for this.

All the steps have been taken, but there is still no solution. BUILTIN\User(SID:S-1-5-32-545) couldnot be found on the target system. New users can not assigned to any group. and new group can not create.

Can I delete this user group [BUILTIN\User(SID:S-1-5-32-545) ] from the registry?

I've never heard of a Repair Install not fixing this. What happened with that?

Please do not skip any steps! We often find out later that the fix was the skipped step. If you need help performing any step I will help.

Yes you can delete the User group, but you'll need to create a new Local User group:

https://www.itechtics.com/add-user-to-group/

https://10scopes.com/enable-local-users-and-gro...

Let me know if you have any questions or I can help performing any of the above steps. If you'll post back detailed results it will help me determine what else needs to be tried.
____________________________________________

Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.

The repair and installation process is normal. However, problems persist after the installation is complete. Oh, my God!!!

What bug am I running into...

I can't delete the built-in user group!

Is this Home edition of Windows 11? Have you enabled the Local User Group Manager as is required in Home edition?

What is the Group Membership of your Admin account in netplwiz > Properties > Group Membership?

What happens if you try to create a new Local Admin account and add it to the Admin group?

Is this an organization with a bunch of users? If so you should ask this to your System Administrator or at our sister forums for IT Professionals, Q&A forums here: https://docs.microsoft.com/en-US/answers/index....

Microsoft Community is strictly an end-consumer forum. Solutions we give here may conflict with the organization''s Group Policy which we do not use in consumer forums at all.

There are also equally good (and sometimes busier) 3rd party IT Pro forums here:
https://www.techrepublic.com/forums/
https://www.spiceworks.com/

I hope it helps.

____________________________________________
Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.

Windows 11 Professional 。

Users can be added to an administrator group。

Enable the built-in hidden Administrator used only in emergencies:
https://www.elevenforum.com/t/enable-or-disable...

See if Local Users group is populated there. If so create a new Admin account to see if the problem goes away:
https://pureinfotech.com/create-local-administr...

Sign into the new account, test it works correctly, if so Move your files over via C:\Users.

Apps are installed to all Users so they should be no problem.

When ready delete the old account in Settings > Accounts > Family & Other Users, or change it to a Local Account in Settings > Accounts > Your Info > Sign in with a Local Account Instead.
You can change the new account to your Microsoft account if desired in Settings > Accounts > Your Info > Sign in with a Microsoft Account Instead.

Feel free to ask back any questions. If you'll post back detailed results then I may know what to suggest next, if necessary.

______________________________________________

Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.