Windows 10 September Update KB5122878 causes No Operating System found on Acer laptop

John Price 65 Reputation points
2026-09-26T15:11:05.03+00:00

KB5122878 after many reinstallations of Windows 10 ESU consistently crashes a friends Acer laptop. Currently I have left this laptop not enabling ESU updates (KB126256) as I have failed to stop the KB5122878 update installing many times. Am I missing something? Can I stop this one killer update downloading and installing? I have already made the registry edit to stop WindowsUpdate, although I am not confident it works. Any suggestions to save this laptop as safely as possible, currently relying on Malwarebytes.

Windows for home | Windows 10 | Windows update
Answer accepted by question author
SD - IA 180.3K Reputation points Independent Advisor
2026-09-30T14:58:27.5366667+00:00

I see, I think your problem is resolved now and no action is required from your end.

Wanted to ask if you have any other questions?

Was this answer helpful?

1 person found this answer helpful.
0 comments
Answer accepted by question author
SD - IA 180.3K Reputation points Independent Advisor
2026-09-30T08:18:15.7333333+00:00

I have now installed the rogue KB5122878 🙂

That is actually the latest update :)

By any chance, are you from the EU? That may explain why enrollment in ESU was not needed.

Was this answer helpful?

1 person found this answer helpful.
Answer accepted by question author
SD - IA 180.3K Reputation points Independent Advisor
2026-09-29T16:43:10.81+00:00

I also did research on the issue, and it seems that you are right :( There are some specific models before 2016 which aren't compatiable, sorry :(

Was this answer helpful?

1 person found this answer helpful.
0 comments

6 additional answers

Sort by: Most helpful
Most helpful Newest Oldest
  1. John Price 65 Reputation points
    2026-09-28T08:42:51.27+00:00

    Jumping ahead is it that the Security certificate has run out for Secure Boot

    There seems to be no Security certificate update for the Acer V5-571, this looks like case closed.

    https://community.acer.com/en/kb/articles/18840-update-your-secure-boot-certificates-in-june-2026-to-stay-protected?expandedToggles=toggle-notebooks

    Was this answer helpful?

  2. SD - IA 180.3K Reputation points Independent Advisor
    2026-09-28T02:46:53.8933333+00:00

    Hi,

    Sorry for the delay over the weekend.

    Typically, this issue can be resolved by updating the BIOS, which I see is pretty old. Additionally, ACER has removed all the BIOS updates from the website.

    To simplify things, please download and let the update fail once. It will leave a trace for the failure.

    Then, do the following:

    Open your File Explorer and go to your system drive, which is commonly C drive.

    Navigate to Windows>Logs>CBS folder.

    You may need to check the Hidden items option under the View tab in tool bar to show the Logs folder.

    Right-click on the CBS.log file and select Copy.

    Paste it to your desktop.

    Go to your OneDrive account and upload CBS.log from the Desktop.

    Share the link of the CBS log and post it in the next reply.

    Was this answer helpful?

Your answer

Answers can be marked as 'Accepted' by the question author and 'Recommended' by moderators, which helps users know the answer solved the author's problem.