If you are not an IT administrator, see the following topic: Get help with Windows 10 upgrade and installation errors.You can also Submit Windows 10 upgrade errors using Feedback Hub.In most cases, the cause is a driver compatibility issue.To troubleshoot a failed upgrade that has returned a result code of 0x C1900101, analyze the extend code to determine the Windows Setup phase, and see the Resolution procedures section later in this topic.Several log files are created during each phase of the upgrade process.These log files are essential for troubleshooting upgrade problems.By default, the folders that contain these log files are hidden on the upgrade target computer.To view the log files, configure Windows Explorer to view hidden items, or use a tool to automatically gather these logs. The log files are located in a different folder depending on the Windows Setup phase.
An example of this event from a successful upgrade is shown below.
Briefly, the upgrade process consists of four phases: Downlevel, Safe OS, First boot, and Second boot. These phases are explained in greater detail below.
First, let's summarize the actions performed during each phase because this affects the type of errors that can be encountered.
If the general troubleshooting techniques described above or the quick fixes detailed below do not resolve your issue, you can attempt to analyze log files and interpret upgrade error codes.
You can also Submit Windows 10 upgrade errors using Feedback Hub so that Microsoft can diagnose your issue.