How do I update Windows 10 that is installed on an external hard disk?

I have windows 10 installed on an external hard disk using Windows-To-Go. The problem I have now is that all windows updates are failing. I get the notification to update, but every time I ask windows to update, it downloads the updates and restarts only to show that the update has failed.

Why does this happen and how do I fix it?

I get this message when I tried to update recently: "You can't install Windows on a USB flash drive using Setup".

Is the only option I have now is to download the latest image of Windows 10 and re-install windows?

Answer

From Microsoft article, it mentioned “Older Windows 8 or Windows 8.1 Windows To Go workspaces cannot be upgraded to Windows 10 workspaces, nor can Windows 10 Windows To Go workspaces be upgraded to future versions of Windows 10. For new versions, the workspace needs to be re-imaged with a fresh image of Windows.”

Here is link: https://docs.microsoft.com/en-us/windows/deployment/planning/windows-to-go-overview#a-href-idbkmk-wtgdifadifferences-between-windows-to-go-and-a-typical-installation-of-windows

But I found a similar question, check if you could modify the registry key PortableOperatingSystem value from “1” to "0" to do the upgrade.

Here is link. Windows To Go (Windows 10) Upgrade to anniversary update? https://social.technet.microsoft.com/Forums/windows/en-US/9f96f44c-4c14-4a51-87c9-7123a0ad29f5/windows-to-go-windows-10-upgrade-to-anniversary-update?forum=win10itprosetup