Windows 10 Pro 22H2 (build 19045.3803) can't install KB5066791 (target build 19045.6456) and fails with 0x800F081F

MT 0 Reputation points
2026-11-14T01:01:42.8633333+00:00

Please help, I spent many hours and tried everything I can think off. Here a summary of all was I have done either myself or with lots of help from ChatGPT.

The issue

  • Windows 10 Pro 22H2 (build 19045.3803) can't install KB5066791 (target build 19045.6456) and fails with 0x800F081F (CBS_E_SOURCE_MISSING). The system was originally upgraded in place from Windows 7.

Root cause (as far as we established it)

  • CBS reports that HyperV-Compute-Host-merged-Deployment 10.0.19041.3758 is missing a composition: HyperV-Compute-BalancerStats 10.0.19041.1.
  • The live WinSxS\Manifests folder lacks that manifest, even though its sibling 10.0.19041.1 Hyper-V manifests are present.
  • The clean Microsoft image has the manifest but no registration or component directory for it.
  • CBS has no registration for it either, and that registry-level gap is the real blocker.
  • The KB5066791 package (all four cabs, checked directly) does not contain it, so the update can't supply it.
  • CBS fails at its own dependency analysis (PerformChangeAnalysis, STATUS_SXS_ASSEMBLY_NOT_FOUND) before it ever asks a source for files.

What was tried

Attempt Result
DISM/SFC RestoreHealth from a clean source Didn't restore it
-------- --------
DISM/SFC RestoreHealth from a clean source Didn't restore it
Disabling Hyper-V and related features They were already disabled
/disable-feature ... /remove on all 12 features All succeeded, but the failure didn't change
startcomponentcleanup Succeeded, no effect
Windows Update and the standalone .msu Same failure. A placeholder path I gave you earlier caused two meaningless 0x80070032 errors
In-place repair upgrade ("keep files and apps") Completed, no change (the ISO was the same 3803 build)
Re-enable Hyper-V from the ESD (wim: and esd: forms) Error 14003, same missing composition
Hand-copying the manifest into WinSxS\Manifests Still 14003, still the same missing composition

Where that leaves things

Everything that works from inside the component store has been exhausted. Hand-editing the COMPONENTS registry hive is the only remaining in-place route, and I advised against it because of the boot risk. The repair options left are a Reset this PC with cloud download, an in-place upgrade from newer media, a clean install, or Windows 11.

Windows 11 and hardware

  • Machine: i5-6600K, ASUS Z170-P board, Radeon RX 480, 8GB RAM, Legacy BIOS with MBR disks.
  • Windows 11 compatibility: TPM 2.0 is present, but the CPU is unsupported. A newer CPU can't fix that, because Z170 boards don't take 8th-gen or later chips.
  • Windows 11 on this PC: only possible through an unofficial bypass, plus an MBR-to-GPT conversion and a switch to UEFI.
  • Support status: Windows 10 is past end of support. I believe consumer ESU ends around Oct 13, 2026, but that is unverified.

Troubleshoot KB5066791 Failure while updating Windows 10

So we now have a fairly strong chain of evidence:

  • CBS says Hyper-V's HyperV-Compute-Host-merged-Deployment requires HyperV-Compute-BalancerStats 10.0.19041.1.
  • The corresponding manifest exists in the clean Microsoft installation image.
  • It does not exist in the live C:\Windows\WinSxS.
  • It is not represented in the live CBS package registry.
  • It is also not represented in the clean image's CBS package registry, which is expected for this kind of component.
  • DISM/SFC source repair did not restore it.
  • KB5066791 fails with the same missing component/source condition. The clean Microsoft image contains exactly one BalancerStats manifest, alongside the related Hyper-V Compute manifests. In particular:
    • HyperV-Compute-BalancerStats — 10.0.19041.1
    • HyperV-Compute-Host-merged-Deployment — 10.0.19041.3758
    • HyperV-Compute-Host-Service — 10.0.19041.3758
    • several other Hyper-V Compute deployment components at 10.0.19041.3636.

That fits the CBS failure we already captured: the 3758 Host-merged deployment is trying to resolve the 10.0.19041.1 BalancerStats composition, and that composition is absent from the live installation. One interesting detail is that the clean WIM also has only the BalancerStats manifest, not a corresponding WinSxS component directory. That suggests we should not assume the missing repair consists of copying a conventional component directory. What we've established

  1. Live Host-merged deployment manifest is intact and byte-for-byte identical to the clean Microsoft WIM.
  2. Live BalancerStats manifest is absent.
  3. Clean WIM contains the BalancerStats manifest, but no corresponding component directory.
  4. CBS specifically identifies HyperV-Compute-BalancerStats 10.0.19041.1 as a missing composition during the Hyper-V transaction.
  5. The same missing composition is implicated in the KB5066791 0x800F081F failure.

The next question is therefore not "is the BalancerStats manifest corrupt?" but: Can CBS repair/register this exact missing assembly from the clean WIM's manifest, or does it require a package/component payload that the current ISO doesn't expose?

  • The clean WIM's SxS Winners registry has no entry containing the BalancerStats hash/identity bbdd6221eec4bf80 Manifest exists in Microsoft's clean WIM: yes.
  • Manifest exists live: no.
  • SxS Winner registration in clean WIM: no.
  • CBS package registration: no.
  • Component directory: no.
  • Parent Host-merged deployment manifest: present and identical on both systems.
  • Clean WIM: BalancerStats manifest exists.
  • Live Windows: exact manifest is absent.
  • Clean WIM: no
  • BalancerStats CBS package registration or SxS Winner registration. Live: no
  • BalancerStats registration either.
  • Host-merged deployment manifest: identical between clean WIM and live installation.
  • CBS: explicitly identifies BalancerStats 10.0.19041.1 as the missing composition.
  • KB5066791: fails with 0x800F081F at the same missing composition.

We now have:

  • Installed: Windows 10 Pro 22H2, build 19045.3803 - Edition: Professional
  • DISM: 10.0.19041.3636
  • Confirmed missing CBS composition: HyperV-Compute-BalancerStats 10.0.19041.1
  • Clean Microsoft WIM: contains the corresponding BalancerStats manifest
  • Live CBS: has no BalancerStats component registration
  • The previous minimal-source RestoreHealth did not register/restore it.

MT.

Windows for home | Windows 10 | Windows update
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2 answers

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  1. Ramesh Srinivasan 90,210 Reputation points Independent Advisor
    2026-11-14T03:13:56.6933333+00:00

    Hi,

    Since you've already tried a repair installation using the ISO and didn't fix the issue, I think the CBS configuration is corrupt.

    Please run DISM again and upload the CBS logs. The logs are available in the following folder. Copy the following folder to the desktop.

    c:\windows\logs\cbs

    Zip the folder and share the file on OneDrive or GoFile.io. Post the link here.

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  2. AI answer

    2026-11-14T01:02:49.42+00:00

    Use Reset this PC → Keep my files → Cloud download as the next supported recovery step; the DISM, feature-removal, manual-update, and same-build repair paths already attempted have not reconstructed the missing CBS metadata.

    KB5066791 does not document 0x800F081F as a known issue. Microsoft defines that code as CBS_E_SOURCE_MISSING, and DISM checks not only WinSxS files and manifests but also the COMPONENTS, Schema, and Component Based Servicing registry data.^1^ This is consistent with a damaged installation-specific component-store state, rather than a published KB5066791 defect.^2^

    1. Create a full backup first, including application data, installers, licence information, and anything outside normal profile folders.
    2. If BitLocker/device encryption is active, record the recovery key.
    3. Open: Start → Settings → Update & Security → Recovery.
    4. Under Reset this PC, select Get started.
    5. Select Keep my files.
    6. Select Cloud download, not Local reinstall.
    7. Review the listed applications that will be removed, then proceed.
    8. Do not interrupt apparently idle or black-screen phases; Microsoft notes that the screen can remain black for an extended period and that manually restarting can cause Reset to fail.^3^
    9. After Reset completes, run Windows Update and verify the build with winver.

    Keep my files preserves personal files but removes installed applications and settings. Cloud download obtains a fresh Windows copy instead of relying on the possibly damaged local recovery files.^3^

    Less disruptive option before Reset

    A second in-place reinstall is reasonable only if Media Creation Tool now supplies installation media newer than the build 19045.3803 previously used. This differs materially from repeating the repair with the same old ISO.

    1. Create current Windows 10 media with Microsoft’s Media Creation Tool.^4^
    2. While booted normally into Windows, mount/open the media and run setup.exe—do not boot from the USB.
    3. Select Change what to keep → Keep personal files and apps → Install.
    4. Confirm before installation that Setup will install Windows 10 Pro and retain apps/files.

    Microsoft documents that this in-place method preserves data, applications, and settings.^5^ If Setup offers only the same servicing level, cannot retain apps, or another repair completes without changing the CBS failure, proceed to Cloud Reset rather than repeating it.

    Avoid manual CBS registration

    Do not import entries into the COMPONENTS hive or manufacture SxS registrations from another installation. A component-store component can encompass files, directories, registry keys, services, manifests, and package relationships; copying one manifest or adding an inferred registry key does not reconstruct that servicing state.^6^

    The clean image’s lack of a conventional component directory or obvious winner/package entry also means there is insufficient public information to derive a safe registration transaction. An offline backup would reduce recovery risk but would not make that edit a supported repair.

    If Reset also fails

    Perform a clean Windows 10 installation from installation media. This removes personal files, applications, settings, and manufacturer customizations, so verify the backup before booting from the USB.^5^

    Support and Windows 11 implications

    Windows 10 support ended on October 14, 2025. Microsoft states that Consumer ESU can protect eligible Windows 10 devices through October 12, 2027, not October 2026.^7^ Installing an October 14, 2025-or-later security update such as KB5066791 is itself an ESU preparation prerequisite, so this servicing failure must be resolved before that path can proceed.^8^

    For Windows 11, supported hardware must have an approved processor, UEFI/Secure Boot capability, and TPM 2.0.^9^ Microsoft does not recommend installing Windows 11 on ineligible hardware; such installations are unsupported and are not guaranteed updates.^10^

    References

    1. Fix Windows Update corruptions and installation failures
    2. October 14, 2025—KB5066791 (OS Builds 19044.6456 and 19045.6456) | Microsoft Support
    3. [Windows 10](https://support.microsoft.com/windows/experience/backup-recovery/reset-your-pc#reset-options)
    4. [Windows 10](https://support.microsoft.com/windows/deployment/install-upgrade/create-installation-media-for-windows)
    5. Reinstall Windows with the installation media | Microsoft Support
    6. Manage the Component Store
    7. Windows 10 support has ended on October 14, 2025 | Microsoft Support
    8. Extended Security Updates (ESU) Licensing Preparation Package for Windows 10 | Microsoft Support
    9. Windows 11 System Requirements | Microsoft Support
    10. Windows 11 on devices that don't meet minimum system requirements | Microsoft Support
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