Fix Error 0xa0000400 When Upgrading to Windows 11

Many users Windows who wish to upgrade to Windows 11 using the Windows 11 Setup Wizard are stopped dead in their tracks by the error 0xa0000400This is reported to occur on a wide variety of different configurations, but the problem seems to be much more prevalent on workstations.

After looking at dozens of different user reports, it's clear that this error has a couple of different causes that could be responsible for this stumble when trying to use the Windows Update Assistant utility. Windows to install Windows 11To find out more, continue reading.

What causes error 0xa0000400 in Windows 11?

Below is a short list of possible scenarios that could cause this problem:

• Conflict with the Virtual Box tool or VMWare: if you have the tool Virtual Box or VMWare installed on your previous version of Windows, you will need to take There and uninstall the utility completely before using the Windows Update Assistant to upgrade to Windows 11. In this case, the error is most likely caused by a conflict between Virtual Box or VMWare and Hyper-V functionality.
• Windows Update Assistant Error: Ironically, for a utility that was developed for the sole purpose of updating the OS From older Windows to Windows 11, the Windows Update Assistant is less successful in doing so. Many users who faced this issue while using the WUA utility eventually managed to complete the upgrade process by upgrading directly by mounting a compatible Windows 11 ISO or by using the Media Creation Tool.
• License key is affecting workstation upgrade: If you're experiencing this issue when trying to upgrade a workstation machine to Windows 11, you can likely avoid the error by changing the current license key to a generic PRO equivalent.

How can I fix error 0xa0000400 on Windows 11?

Now that you are familiar with all the potential scenarios that could be responsible for this error, let’s move on to the part where we help you fix the problem.

Below you will find four different methods that other users who are in a similar situation have successfully used to get to the bottom of this problem.

Uninstall Virtual Box / VMWare (if applicable)

It turns out that one of the most common causes that cause the 0xa0000400 error when using the Windows Update Assistant is a conflict between Hyper-V and the proprietary virtualization technologies present with Virtual Box and VMware.

In case you are trying to upgrade to Windows 11 and you have Virtual Box or VMWare installed on your previous versions of Windows, the first thing you need to do is install the conflicting software to ensure that the upgrade process is successful.

Nota: Once the Windows 11 upgrade process is complete, you can easily reinstall the virtualization software you are using.

If this scenario is applicable, follow the instructions below to get what you need to get rid of third-party virtualization software that is conflicting with the Windows Update Assistant:

• Press the Windows key + R to open a dialog box Run. Then write 'appwiz.cpl' inside the text box and press Ctrl + Shift + Enter to open the menu Programs and Features with administrator access.

• When you are asked for the User Account Control (UAC), Click on Yes to grant administrator access.
• Once you are inside the Programs and Features menu, scroll down the list of installed programs and locate VMware o virtual Box (depending on the conflicting software you want to uninstall).
• After you manage to find the entry associated with the conflicting software, right-click on it and select uninstall in the context menu.
• Within the uninstallation screen, follow the on-screen instructions to complete the uninstallation process.
• After the conflicting software has been (supposedly) uninstalled, open the Windows Update Assistant tool once again and see if you can now upgrade to Windows 11 without encountering the same 0xa0000400.

In case this method is not applicable to you or you have already tried to uninstall the conflicting software but you still get the same error, continue with the next potential solution.

Perform the upgrade from mounted Windows 11 ISO

If the first method was not applicable, the next thing you should try is to complete the upgrade to Windows 11 by downloading and mounting a compatible Windows 11 ISO.

As of now, WUA (Windows Update Assistant) remains a very buggy utility and should be avoided. You'd be better off mounting an official Windows 11 ISO and performing the upgrade directly by opening setup.exe in the root location of the ISO.

Many users confirm that this method works with the error 0xa0000400 when trying to use the Windows Update Assistant.

Here is the exact process they followed to avoid error 0xa0000400 when upgrading to Windows 11:

• Open your default browser, then visit the Windows 11 official download page.

 

• Once you are inside the correct page, scroll down to the section Download Windows 11 Disc Image (ISO), then select Windows 11 using the button Select download.

 

• Then click on the button Download and wait for the selection to be registered.
• From the next message that just appeared, use the drop-down menu to select your preferred language before finally clicking on Confirm.

 

• Finally, click on the new button Windows 11 English ISO that just appeared to confirm the download.

Nota: Please note that this download link will only be available for 24 hours after clicking the download button.

• Wait for the ISO to download locally, then simply double-click the .iso file to mount it locally.

Nota: There is no need to use third-party tools like Daemon Tools to mount this ISO, as all recent versions of Windows have ISO mounting capabilities natively.

• Once the ISO is mounted locally, open the File Browser and double-click on the virtual drive that just appeared.
• After you are inside the root location of the Windows 11 ISO, double-click setup.exe, then click Yes when requested by the User account control.

• Now, once you're inside the Windows 11 Setup screen, select Download updates, drivers, and optional features (recommended), then follow the remaining instructions to complete the upgrade to Windows 11.

If this method didn't work for you, or if you're looking for a different method, move on to the next potential solution outlined below.

Use the media creation tool to update

If the above method (mounting a Windows 11 ISO file directly) didn't work for you, you can always use MCT (Media Creation Tool) to burn a DVD or convert any flash drive (larger than 8GB) into a compatible Windows 11 installation media.

After doing this, you can change the boot order accordingly and perform the update procedure directly from your flash drive.

Previous requirements: In addition to an Internet connection, you need a blank DVD disc of at least 8 GB and a DVD burner or flash drive of at least 8 GB. storage available.

If you meet one of these requirements and are ready to go down this path, follow the instructions below to use the Media Creation Tool to upgrade to Windows 11 and avoid error 0xa0000400:

• Open your favorite browser and visit the Windows 11 download page.
• Once you are inside the Windows 11 download page, scroll down to the Create Windows 11 installation media section, then click the button download now.

• Wait until the executable is downloaded locally, then double-click it.
• When prompted for the window User account control, click on Yes to grant administrator access.
• Within the Windows 11 installation media creation tool, first accept the License Agreement and then select the edition of Windows 11 for which you want to create installation media.

• On the next screen, select flash drive USB o ISO file, depending on whether you want to create a flash drive or a Windows 11 DVD installation media.

• Follow the remaining prompts to complete creating your Windows 11 installation media, then restart your PC and insert the DVD or connect your flash drive to upgrade to Windows 11.

Nota: Please note that in case you have chosen to create a USB flash drive, you may need to change the boot order from your UEFI or BIOS settings to ensure that your PC boots from the flash drive and not from your HDD or SSD.

If this method is not applicable to you, please move on to the next potential solution below.

Change the license key to PRO version (for workstations only)

If you encounter this issue when trying to upgrade a workstation to Windows 11, you should ensure that you are using a PRO license key before attempting to start the upgrade.

To be clear, you don't need to purchase a new PRO license just to be able to upgrade - you can simply switch to a generic Windows PRO license key before you start the upgrade.

If the update is successful, you can return to your regular license key.

Please follow the instructions below to change the license key to PRO:

• Press the tecla Windows + I to open the screen Configuring Windows.
• Once you are inside the screen Configuration, Click on Update and security in the list of available options.

• Then click Activation from the list of available options, then click the hyperlink Change key product and insert one of the following generic PRO keys (depending on your particular version):

1. Windows 10 Pro: NF6HC-QH89W-F8WYV-WWXV4-WFG6P
2. Windows 10 PRO N: NH7W7-BMC3R-4W9XT-94B6D-TCQG3
3. Windows 10 PRO Education: 8PTT6-RNW4C-6V7J2-C2D3X-MHBPB
4. Windows 10 Pro Education N: GJTYN-HDMQY-FRR76-HVGC7-QPF8P

After the product key has been changed, try upgrading to Windows 11 again and see if the operation now completes without the same 0xa0000400.

Nota: If the upgrade to Windows 11 is successful, you can revert to your previous license key using the same procedure shown above (the steps are almost identical on Windows 11).