If you encounter an error code of 0xa0000400 while trying to upgrade your Windows 10 computer using the Windows 10 Upgrade Assistant or the Windows 10 Media Creation Tool, then you might find this post useful as it will guide you in resolving this problem. When you get this error, you will see the following error message:
“Something went wrong
You can contact Microsoft support for help with this error. Here is the error code 0xa0000400.”
As you know, keeping your computer up to date with all the Windows Updates is important and is imperative especially if you are experiencing a couple of issues like the Windows Upgrade error 0xa0000400. At the time of writing, there is no specific cause that has been found for this error. However, there are some potential fixes that might help you. You can try to recreate the Windows 10 installation USB and get the ISO files or you could also get a newer version of the Windows Media Creation Tool, or turn off your internet connection at a specific time or run the Windows Update troubleshooter. For more details, refer to the options given below.
Recreating the Windows 10 installation USB might help in fixing the problem. You can use a USB drive to do so but make sure that it has a great read-write speed. Follow the steps below to recreate Windows 10 installation USB”
You might want to turn off your internet connection at a specific time. This option can be quite tricky so what you need to do is to disconnect the internet connection when the update is downloaded using the Windows Upgrade tool. It’s actually okay since all the files you need would be downloaded safely and the Windows Upgrade tool will be the one to install the newer updates using those files.
You can also fix the Windows Upgrade error 0xa0000400 by using the latest version of the Windows Media Creation tool. And so if what you have is an older version, you need to update it in order to resolve the error and upgrade your Windows 10 computer.
Running the built-in Windows Update troubleshooter is one of the things you can first check out as it is known to automatically resolve any Windows Update or upgrade errors like error code 0x800701E3. To run it, go to Settings and then select Troubleshoot from the options. From there, click on Windows Update and then click the “Run the troubleshooter” button. After that, follow the next on-screen instructions and you should be good to go.
You might want to run the Disk Cleanup utility as it is a useful tool that could delete temporary and useless files in your computer.

Error 1309. Error reading from file: pathfilename.cab. Verify that the file exists and that you can access it.When installing Microsoft Office 2003, the error message may appear in the following format: Fatal Error During Installation
Error Causes
Error CausesError code 0xc004fc03 occurs when Windows users fail to activate their Windows operating system due to a networking problem. The error code’s common symptoms include the following:
Error CausesError code 0xc004fc03 in Windows 10 usually occurs due to issues related to a Windows user’s network. Your computer may be having problems connecting to the Internet or your firewall may be blocking or interrupting your device’s ability to activate Windows 10. In some cases, users may simply need to wait a day or two to reattempt to activate their system using a valid product key, as there may be an issue with the Windows activation servers. Failure to promptly fix this error code might result in other Windows 10 error messages, such as error code 0xc004f034.
To rectify the error code, Windows 10 users will need to perform manual repair procedures that fix the underlying problems causing error code 0xc004fc03. These procedures may include reconnecting to one’s network, checking your firewall settings, or activating your Windows operating system via phone. The manual repair methods are simple and do not require technical knowledge of the Windows operating system. If your attempts at manually repairing this error code fail, however, you may need to try a few other procedures.
To check your Internet connection, you’ll need to access the Network & Internet tab in Windows 10. Follow the instructions below to access this tab and fix Internet connectivity issues if they are preventing you from activating Windows on your machine.
If your status shows that you are not connected to a network, you will need to fix your connection. Simply use the Network Troubleshooter to troubleshoot your connection. You will be able to activate your copy of Windows once your connectivity issues are resolved.
If, however, the problem persists and error code 0xc004fc03 occurs during the activation process, this simply means that the existence of the error code is not due to connectivity or networking problems. In such a case, move to the next manual repair method listed below and follow the exact instructions given.
Windows Firewall protects your PC from hackers, worms, and other malicious programs. However, in some cases, it may result in error codes like error code 0xc004fc03. If your firewall is interfering with the Windows 10 activation, you’ll be able to rectify the problem by simply adjusting your settings. Follow the steps below to check – and adjust if necessary – your Windows Firewall settings.
In some cases, Windows users may not be able to adjust settings within the Windows Firewall tab, as your firewall settings may be controlled by a third party antivirus software. If this is the case, open the antivirus software and turn off the firewall if the software does not prevent you from making such changes to its settings.
Note, however, that you will need to readjust the settings as soon as you activate your version of Windows 10. This is due to the fact that turning off your firewall settings permanently may lead to exposure to worms and other malicious programs.
Activation of Windows via phone is another option for individuals experiencing error code 0xc004fc03. The activate by phone option in the Update & Security tab will be available once you fail to activate Windows 10. To complete this manual repair method, follow the steps below.
This is one of the most effective ways to fix error code 0xc004fc03. If the issue persists, however, you can proceed to the last resort.
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Error Causes