Windows 11 KB5121003 Installation and Boot Failure Issue

Question

Windows 11 KB5121003 Installation and Boot Failure Issue

Rob 0

I recently purchased a new HP laptop running Windows 11 25H2. I am experiencing repeated problems installing the August 2026 security update KB5121003 (OS Build 26200.9168).

Initial problem

The first time Windows attempted to install KB5121003, the update failed. The computer then showed messages such as:

“Something didn't go as planned. Undoing changes.”
“Attempting repairs.”
“We removed some recently installed updates to recover your device from a startup failure.”

The computer eventually recovered and booted normally.

At first, I was concerned that I may have accidentally interrupted the update because I had left the computer unattended and the display had turned off. I did not realize Windows was performing an update, and I powered the computer off/on. This may have interrupted that particular update attempt.

Windows repair checks

I then followed troubleshooting steps to determine whether Windows itself was corrupted.

I ran:

DISM.exe /Online /Cleanup-image /Restorehealth

DISM completed with:

“The restore operation completed successfully. The operation completed successfully.”

I then ran:

sfc /scannow

SFC completed with:

“Windows Resource Protection did not find any integrity violations.”

Therefore, both DISM and SFC completed successfully and did not identify any remaining Windows system-file corruption.

Second attempt

Windows Update later attempted KB5121003 again.

The update initially appeared to install successfully. However, after restarting, the computer experienced an unusual boot process involving memory training. The memory-training screen remained for approximately 10 minutes.

I eventually powered the computer off and back on. It then successfully booted into Windows.

I restarted it again afterward to make sure the memory-training screen would not appear again. On that subsequent restart, the computer booted normally.

However, when I checked Windows Update again, KB5121003 was being offered again as if it had not remained installed.

I checked the Windows build and found that the system was still on OS Build 26200.8875, rather than the expected 26200.9168.

Another automatic update attempt

The following day, Windows automatically attempted the update again.

Windows requested a restart, and I allowed it to restart normally. During the update/restart process, I saw a progress percentage (approximately 7%), after which the screen went black and displayed only the HP logo.

The HP logo remained on the screen for approximately 50 minutes without progressing.

Because the computer appeared to be completely stuck, I eventually powered it off and turned it back on. Windows then entered Automatic Repair, successfully recovered, and eventually returned me to the Windows desktop.

After this, KB5121003 showed:

Install error - 0x800f0845

Windows Update troubleshooter

I also ran the Windows Update troubleshooting process through the Get Help application.

It reported:

“Problem detected. Good news! We detected a problem and have attempted to resolve it. Windows Update will now scan and attempt to install any missing updates.”

The troubleshooter therefore detected an actual Windows Update problem and attempted to repair it.

Current situation

The main issue is that KB5121003 repeatedly fails to install/complete, particularly during the restart portion of the installation.

The computer is able to boot normally after recovery, and I have not experienced general Windows corruption.

The most concerning behavior is that the computer sometimes remains at the HP logo for an extended period during the reboot required to install KB5121003, followed by Automatic Repair and rollback when the computer is restarted.

Troubleshooting already performed

Ran Windows Update troubleshooter/Get Help
Ran DISM.exe /Online /Cleanup-image /Restorehealth
DISM completed successfully
Ran sfc /scannow
SFC reported no integrity violations
Allowed Windows Update to automatically retry the update
Allowed the computer to restart normally for the update
Checked Windows build with winver
Current/previous build remained 26200.8875 after failed/rolled-back attempts
KB5121003 has repeatedly been offered again after the failed installations

What I would like help determining

I would like to know:

Why KB5121003 is failing during the reboot/installation phase.
What specifically causes error 0x800f0845 in this situation.
Whether the extended HP-logo screen is related to the Windows update, BIOS/firmware, memory training, or another hardware/driver issue.
Whether there is a known compatibility issue between KB5121003 and this HP laptop/model.
What Microsoft recommends as the next troubleshooting step before I consider returning/exchanging the laptop.

The laptop is brand new and is still within its return period, so I would especially like to determine whether this is a Windows Update/software issue or a potential hardware/firmware problem before deciding whether to keep the laptop.

Laptop information:

Laptop: HP OmniBook X Flip 2-in-1
Model: 16-cc0003dx / D31MMUA#ABA
Display: 16" 2K touchscreen
Processor: AMD Ryzen AI 5 430
Memory: 16 GB onboard RAM
Storage: 512 GB NVMe SSD
Operating System: Windows 11 Home
Device: Copilot+ PC
Color: Meteor Silver

Kim File 0 Reputation points

2026-08-24T23:11:40.7033333+00:00

My granddaughter's new laptop experienced the same failure on this update. It's also an HP Omnibook X Flip, model 14-KC0013DX, 14-inch 2-in-1 convertible AI touch laptop featuring an AMD Ryzen AI 5 processor, a 2K OLED touchscreen, 16GB of RAM, and a 512GB SSD.

The initial failure happened with the August preview version, and we were unable to get that to install correctly even after performing the same recovery methods mentioned in this post. The issue occurred again after trying to update with the released version of the update.

We're anxiously awaiting to see if someone identifies a solution to this.
Rob 0 Reputation points

2026-08-25T03:54:34.6+00:00

I ended up exchanging my laptop for a replacement. However, when I went back to the store, I checked the display model of the same laptop and noticed that it was also showing the failed update.

Because of that, I’m expecting my replacement, which should arrive sometime tomorrow, to potentially have the exact same issue. If it does, I may have to consider switching to a different laptop altogether if Microsoft does not release a fix for this update within a few days.

So if you’re still within your return or exchange period, it may be worth keeping that in mind and considering your options as well. Hopefully Microsoft is able to identify the cause and release a fix soon.

4 answers

Your answer

Kim File 0 Reputation points

2026-08-24T23:11:40.7033333+00:00

My granddaughter's new laptop experienced the same failure on this update. It's also an HP Omnibook X Flip, model 14-KC0013DX, 14-inch 2-in-1 convertible AI touch laptop featuring an AMD Ryzen AI 5 processor, a 2K OLED touchscreen, 16GB of RAM, and a 512GB SSD.

The initial failure happened with the August preview version, and we were unable to get that to install correctly even after performing the same recovery methods mentioned in this post. The issue occurred again after trying to update with the released version of the update.

We're anxiously awaiting to see if someone identifies a solution to this.
Rob 0 Reputation points

2026-08-25T03:54:34.6+00:00

I ended up exchanging my laptop for a replacement. However, when I went back to the store, I checked the display model of the same laptop and noticed that it was also showing the failed update.

Because of that, I’m expecting my replacement, which should arrive sometime tomorrow, to potentially have the exact same issue. If it does, I may have to consider switching to a different laptop altogether if Microsoft does not release a fix for this update within a few days.

So if you’re still within your return or exchange period, it may be worth keeping that in mind and considering your options as well. Hopefully Microsoft is able to identify the cause and release a fix soon.

Answer 1

I’m having the same issue on a brand-new HP OmniBook X Flip 16 (16-cc0013dx) with:

AMD Ryzen AI 5 430
16 GB RAM
512 GB SSD
Windows 11 25H2

The problem happens specifically when installing 2026-08 Security Update KB5121003 (26200.9168).

The update downloads and installs normally until the required restart. After restarting, the laptop gets stuck indefinitely on the black HP logo screen with no spinning circle. Eventually, after forcing a restart, Windows either enters Automatic Repair or rolls back the update.

After rollback, Windows boots normally again and Windows Update shows:

KB5121003 — Install error 0x800f0845

I have reproduced this multiple times.

Answer 2

CrazyKats 18,230 Volunteer Moderator

Hi Rob,

I would Pause Updates.

Open Task Manager/Services and

Stop the Windows Update Service.

Reboot the PC and see if it finds

the newest update 26200.9267.

Hope it works.

0 comments

Answer 3

Carl-L 20,565 Microsoft External Staff Moderator

Hello Rob, Kim File

Welcome to Microsoft Q&A forum.

May I know if the AI assistant suggestion works for you? If it doesn't may I know how it goes?

Before we proceed further, can you please go to the Microsoft Update Catalog and try to find and download the KB there to manually install it? Also, please submit feedback to the Feedback Hub in your Windows computer, it will be delivered directly to the engineering team so they can apply a fix in a future update.

I'm waiting for your reply.

Rob 0 Reputation points

2026-08-25T14:55:53.7033333+00:00

Hello,

Thank you for your response. I have not yet tried manually downloading and installing KB5121003 from the Microsoft Update Catalog, but I can try that and report back with the results.

I also wanted to provide an important update. I ended up exchanging my original laptop for a replacement because of this issue. However, while at the store, I checked a display model of the exact same HP OmniBook X Flip, and it was also showing that KB5121003 had failed to install.

In addition, another user in this discussion has reported experiencing a very similar issue on their granddaughter's HP OmniBook X Flip with the same update. Because multiple HP OmniBook X Flip systems appear to be experiencing problems with this update, I am becoming increasingly concerned that this may be a compatibility issue cause this rules out any individual laptop issues.

My replacement laptop is expected to arrive later today. I will check whether KB5121003 also fails on the replacement and will also try the Microsoft Update Catalog installation as you suggested. I will report back with the results.

I will submit feedback through the Feedback Hub as well.

Thank you for your help.
Eric Carlson 0 Reputation points

2026-08-26T03:27:38.1066667+00:00

I did download the KB from the Microsoft Update Catalog, and it gave the exact same error as before. For me, it gets to 36%, on the second reboot, and then rolls back,. I get error 0x800f0922 which might be another clue.
Carl-L 20,565 Reputation points Microsoft External Staff Moderator

2026-08-26T13:39:42.7933333+00:00

Hello Rob, Eric Carlson,

Thanks for letting me know.

I see there is another user suggestion above, can you please follow it first and tell me how it goes?

Answer 4

The supported facts point to a Windows Update installation failure during the reboot phase, not confirmed Windows file corruption.

Based on the completed checks already run:

DISM.exe /Online /Cleanup-image /Restorehealth completing successfully means the Windows image repair completed successfully.
sfc /scannow reporting no integrity violations means System File Checker did not find remaining system file corruption.
The Windows Update troubleshooter in Get Help is the recommended first step on Windows 11 and can detect and attempt to fix common update problems.

For the failure itself, the available guidance supports these next steps:

Run the Windows Update troubleshooter again from Start > Settings > System > Troubleshoot > Other troubleshooters > Windows Update > Run if it is still being offered.
Check available storage. Windows requires at least 16 GB free space for 32-bit or 20 GB for 64-bit upgrades. Low space can block update completion.
If the update stalls again during installation, try Start > Settings > Windows Update > Check for updates and install any newer update that replaces the failing one.
Perform a clean restart of Windows to reduce software conflicts from startup apps and non-Microsoft services.
If the problem continues, use the advanced Windows Update reset steps from an elevated Command Prompt:
- net stop bits
- net stop wuauserv
- ren %systemroot%\softwaredistribution softwaredistribution.bak
- ren %systemroot%\system32\catroot2 catroot2.bak
- net start bits
- net start wuauserv Then restart the PC.
If third-party antivirus or security software is installed, temporarily uninstall it before retrying the update. Reinstall it after the device is updated.
Run a disk repair check from an elevated Command Prompt: chkdsk /f C:. This requires a restart.

What can be concluded from the provided information:

The context does not provide a documented cause for error 0x800f0845.
The context does not identify a known compatibility issue for KB5121003, the HP OmniBook X Flip 16-cc0003dx, or the described HP logo / memory training behavior.
The context does not confirm whether the long HP-logo screen is caused by Windows Update, BIOS or firmware, memory training, or hardware.

One documented reboot-phase update failure pattern in current Windows release health is for error 0x800f0922, where installation can fail around 35–36% and roll back because of insufficient free space on the EFI System Partition (ESP). That specific issue was resolved by later updates, but it shows that reboot-phase rollback can be caused by boot-related partition space problems. That is not the same as 0x800f0845, but it is relevant to the type of failure being observed.

Before considering return or exchange, the supported next troubleshooting path is:

Ensure sufficient free disk space.
Retry through Windows Update after running the troubleshooter.
Perform a clean restart.
Reset Windows Update components by renaming SoftwareDistribution and Catroot2.
Run chkdsk /f C:.
If the issue still persists, a clean installation of Windows 11 is a documented last-step option. This is higher risk because it changes the installation state and requires careful preparation.

If the device continues to fail only during update reboot after those steps, the provided context does not contain a more specific Microsoft-documented root cause for this exact update and model.