"Bad image" error after downloading Windows 11. Attempted to resolve the issue by following a solution on another question. Now Windows Security opens, shows the logo, then closes after 2-3 minutes.

Hi, I'm Bernard. I'm happy to help!

May I know how you ran a repair and reinstall? Is it through Windows Settings? If yes, I suggest doing an in-place upgrade, wherein it will upgrade the device to the latest version and repair all issues without deleting any files.

Go to the Windows 11 website: https://www.microsoft.com/en-us/software-download/windows11

Under Download Windows 11 Disk Image (ISO), select Windows 11 (multi-edition ISO)

1.    Once done downloading the ISO, kindly right-click on the ISO, then click Mount> click Setup.exe

2.    You may be prompted by User Account Control. Click on Yes if so

3.    In the Install Windows 11 dialog, click Next

4.    Setup will check your PC and show a license agreement. Click on Accept in the license terms dialog.

5.    Wait for the setup program to check for the available free space.

6.    On the Ready to install page, make sure Keep personal files and apps have been checked.

7.    Then click Install and just follow the prompt.

8.    Windows 11 will restart your device several times and lead you to the lock screen. Depending on the options you set, it will keep all your files, apps, and user accounts.

For reference: https://learn.microsoft.com/en-us/answers/questions/4252110/how-to-run-in-place-upgrade-in-windows-11

Note: This is a public forum. I may respond shortly, but I apologize in advance for any delays. I am simply a fellow user trying to provide helpful insights and information.

Replacing system DLLs from untrusted or archived sources can corrupt Windows components like Windows Security. Use in-place repair options and Windows Update to restore the original files and fix Windows Security without a full reinstall.

1. Run a repair install of Windows 11 (keeps apps and files)
   • Open Settings > System > Recovery.
   • Select the option to Reinstall or Repair install Windows (this reinstalls the current Windows 11 version while preserving apps, files, and most settings).
   • Let the process complete and then restart.
   • After the repair, open Windows Security again and confirm it stays open.
2. Make sure Windows is fully updated
   • Go to Start > Settings > Windows Update.
   • Select Check for updates and install all available updates.
   • Restart if prompted and test Windows Security again.
3. If Windows Update has issues
   • Open Command Prompt as administrator.
   • Run these commands one by one to reset update components:

          net stop bits
          net stop wuauserv
          ren %systemroot%\softwaredistribution softwaredistribution.bak
          ren %systemroot%\system32\catroot2 catroot2.bak
          net start bits
          net start wuauserv
     

   • Restart the PC and run Windows Update again.
4. If Windows still shows security issues
   • Use the built-in Windows troubleshooters and, if needed, repeat the repair install step to restore any remaining damaged system files.

These steps restore official system binaries (including SecurityHealthSSO.dll) and are safer and more complete than manually copying DLLs.

References:

• Troubleshoot problems updating Windows
• Troubleshooting Windows unexpected restarts and stop code errors
• Windows 11 File Explorer only previews PDF files in file preview pane as thumbnails. - Microsoft Q&A
• HOW CAN Windows 11, version 25H2 Install error - 0x800f081f BE FIXED? - Microsoft Q&A
• windows 11version 25H2 couldn't install, error 0x80070476 - Microsoft Q&A
• Automatically fix Windows security issues