Fix: The Computer Restarted Unexpectedly or Encountered an Unexpected Error on Windows

In some cases, when you perform a clean installation of Windows, update a build, or create a reference image using sysprep, the Windows Installer fails with an error: The computer restarted unexpectedly or encountered an unexpected error. Windows installation cannot proceed. When you click OK, the computer restarts, and when you re-run the Windows Setup, you see the same error window repeatedly in a loop… If your computer keeps restarting unexpectedly, what can you do to proceed with Windows installation?

The error may occur during one of the stages of installing or updating Windows, and looks like this:

The computer restarted unexpectedly or encountered an unexpected error. Windows installation cannot proceed. To install Windows, click “OK” to restart the computer, and then restart the installation.

Neither clicking the OK button nor restarting the Windows installation wizard helps when the “Computer restarted unexpectedly” error occurs. The error goes into a never-ending loop.

To fix the problem, you don’t have to close the error message or click OK, and follow these steps:

1. Press Shift + F10 right on the screen with the error. On some laptops, you may need to use a different keyboard shortcut: Shift+Fn+F10;
2. This will open a command prompt window. From here, you need to open the registry editor by running the regedit command;
   
3. Got to the registry key HKEY_LOCAL_MACHINE\SYSTEM\Setup\Status\ChildCompletion
4. In the right pane, locate the setup.exe parameter. Its value is likely to be 1. Change it to 3 and save the changes;
   Note. This value forces the Windows Installer to proceed to the next stage of the operating system installation
   
5. Close the Registry Editor, and restart your computer by clicking OK in the error windows or using the command: shutdown -r -t 0 or wpeutil reboot

After the computer restart, the Windows installation (update) process should proceed normally.

The issue of Windows installation being interrupted by an unexpected restart can occur in Windows 10 and 11, as well as previous versions of Windows and Windows Server.

If the above method does not help you resume a normal Windows installation and fix the automatic restart problem, try the following solutions.

1. Boot your computer from any Windows installation media or a LiveCD;
2. Press Shift + F10 on the first installation screen to open the command prompt;
3. You need to know the drive letter assigned to your Windows volume;
4. Run the commands:
   diskpart
List vol
   In my example, the Windows is located on Volume 1 (according to partition size). No drive letter is currently assigned to this partition. Let’s assign the drive letter W manually:
   Assign letter=w:
exit
   
5. Run regedit and load the HKEY_LOCAL_MACHINE\SYSTEM registry hive from your offline Windows image;
6. Select the HKEY_LOCAL_MACHINE in the Registry Editor and click the File -> Load Hive. Select the file W:\Windows\System32\Config\System
7. Set the hive name (mylocal). This will load your offline Windows image’s HKLM registry key into the registry editor;
8. Go to the reg key HKEY_LOCAL_MACHINE\Mylocal\Setup\Status\ChildCompletion and change the value of the setup.exe parameter to 3 
9. To save changes to the offline registry file, select File-> Unload Hive
10. Switch to the WinPE command prompt and restart the computer using the command: wpeutil reboot
11. The Windows installation will then continue normally.

Solution: burn the original Windows installation media using the official Media Creation Tool or Rufus (How to create a bootable UEFI USB drive with Windows Setup).

Run a clean installation of Windows from a new bootable USB stick, and be sure to delete all partitions on the drive you want to install Windows on (if you have your data on the drive, copy it before removing the partitions). Continue to install Windows on the Unallocated space. Windows Installer will create all the necessary system partitions (read more about system EFI and MSR partitions in Windows).

Also:

• Check your local hard drive for errors: chkdsk W: /F /R
• Disconnect all unused USB drives, LAN, and Wi-Fi network adapters from the computer (physically or in the BIOS/UEFI settings).