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KB5066791 fails

douglas wozniak 20 Reputation points
2025-11-05T19:22:35.9+00:00

aloha

have been trying to install KB5066791 for several weeks.

have tried dozens of times.

it gets to 8% then fails.

so, cannot activate ESU.

KB5065429 is installed instead of KB5066791.

restart popup window comes up several times a day.

cheers

Windows for home | Windows 10 | Windows update
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  1. Carlo Luna 6,895 Reputation points Independent Advisor
    2025-11-05T20:09:00.89+00:00

    Hi Douglas,

    Thanks for sharing the details about KB5066791. I understand how frustrating it is when an update keeps failing after multiple attempts, especially since it blocks ESU activation and triggers frequent restart prompts.

    This usually happens if prerequisites are missing, update components are corrupted, or the system defaults to an alternate update like KB5065429.

    I'd suggest checking your update history for any error codes related to KB5066791. Then, run the Windows Update Troubleshooter under Settings > Update & Security > Troubleshoot to repair common issues. If that doesn’t work, download KB5066791 from the Microsoft Update Catalog and install it manually.

    For persistent failures, performing an in-place upgrade using the Media Creation Tool can refresh system files without affecting your apps or data.

    I hope you find this information helpful. Please let me know if you have any further questions If the answer is helpful, please click "Accept Answer".

    Regards,
    Carlo

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  2. douglas wozniak 20 Reputation points
    2025-11-05T20:58:16.87+00:00

    went to "Microsoft Update Catalog"

    selected

    ||2025-10 Cumulative Update for Windows 10 Version 22H2 for x64-based Systems (KB5066791)| | -------- | -------- | no joy.

    same same.

    any other ideas?

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  3. douglas wozniak 20 Reputation points
    2025-11-05T20:47:55.46+00:00

    no joy.

    same same.

    "Failed to install on ‎11/‎5/‎2025 - 0x80070490"

    what the heck does that mean?

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  4. douglas wozniak 20 Reputation points
    2025-11-05T20:05:31.3933333+00:00

    have tried everything anyone has suggested.

    no joy.

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  5. AI answer

    2025-11-05T19:22:49.6433333+00:00

    It seems like you're experiencing issues with installing the KB5066791 update, which is preventing you from activating Extended Security Updates (ESU). Here are some steps you can take to troubleshoot the problem:

    1. Check for Prerequisites: Ensure that all prerequisite updates for ESU are installed. Sometimes, missing prerequisites can lead to installation failures.
    2. Restart Your Computer: Since you mentioned that the restart popup comes up frequently, make sure to restart your computer after installing any updates or changes.
    3. Run Windows Update Troubleshooter: Use the built-in Windows Update Troubleshooter to diagnose and fix issues related to Windows Update.
    4. Check Update History: Look at the update history to see if there are any error codes associated with the failed installation of KB5066791. This could provide more insight into the issue.
    5. Free Up Disk Space: Ensure that you have enough disk space available, as insufficient space can cause updates to fail.
    6. Manual Installation: If the update continues to fail, consider downloading the update manually from the Microsoft Update Catalog and installing it.
    7. Contact Microsoft Support: If the issue persists, it may be best to reach out to Microsoft Support for further assistance.

    Following these steps should help you resolve the installation issue with KB5066791.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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