Fix Error Code 0xc1900101 while upgrading to Windows 11 using Windows 11 Installation Assistant. It's usually a driver issue that needs to be fixed.

Before we go ahead, it is interesting to note that errors like 0xC1900101 – 0x400xx occur on the final page of the upgrade, i.e., when Windows boots for the first time and configures settings.

A generic Windows error may prevent users from updating until Microsoft releases a fix.