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Windows 11 Installation Assistant fails and reverts to Windows 10 during installation

Jacob Worgan 20 Reputation points
2025-10-03T12:44:41.3366667+00:00

setupact.logI have made sure that my system is compatible with Windows 11 through the PC Health Check, having enabled TPM 2.0 in BIOS.

Windows update says that the PC is compatible, but gives no direct option to upgrade to Windows 11, so I have used the Windows 11 Installation Assistant.

However, while it downloads, verifies, and installs, when it restarts the PC and goes through the final installation, it gets to around 12% and then stops and reverts to Windows 10.

So far I have done a clean boot of Windows, enabled memory integrity (which required removing a few outdated bluetooth drivers), and checked that the hard disc is using the GUID partition style. None of these have made any difference to the outcome.

Attached is the setupact file in the C:$WINDOWS.~BT\Sources\Rollback folder for context.

Any help would be appreciated as I have run out of things to try that I can find online.

Windows for home | Windows 10 | Windows update
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Answer accepted by question author

David Dawson 246 Reputation points
2025-10-03T16:14:25.6833333+00:00

I don't know if it'll help without looking at logs but first thoughts are:

  • Space consideration? 64 GB is required for Win11 but I'm not sure how much space is needed for upgrade.
  • Download full ISO and run from there. Anecdotally this seems to succeed when normal downloader fails.

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  1. David-M 113.9K Reputation points Independent Advisor
    2025-10-03T13:26:21.08+00:00

    Hi. I'm David, and I'm happy to help you.

    One of the critical errors identified in the logs is "0x80070005", which generally indicates access denied, a permissions-related issue. This can stem from restricted access to system files, registry entries, or interference from third-party security software. Additionally, the logs contain warnings about missing or inaccessible system files, which may have contributed to the installation failure and subsequent rollback.

    Please clarify the following:

    Do you have a third-party antivirus installed? If yes, which one?

    Also. What is the current "OS Build" of your Windows 10?

    • Press "Windows + R", type winver, and click OK.

    If you prefer, share a screenshot. Use the shortcut "Windows + Shift + S" to use the screenshot tool.

    Be sure to censor your email address if it appears. The Microsoft Q&A is public.

    I await your reply.

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