I ran into error while reinstalling Microsoft Windows 10 Pro on Lenovo T420 laptop.
The computer restarted unexpectedly or encountered an unexpected error. Windows installation cannot proceed...
Doubleclick on Setup.exe on the right pane, change Value data from 1 to 3, press OK.
Press OK again to close Install Windows dialog.
Reboot. The installation will continue.
The computer restarted unexpectedly or encountered an unexpected error. Windows installation cannot proceed...
Workaround
Press SHIFT + F10 to open Command line windows.
Run regedit.exe to open Registry Editor
Go to Computer\HKEY_LOCAL_MACHINE\SYSTEM\Setup\Status\ChildCompletion
Look for Setup.exe on the right pane
Doubleclick on Setup.exe on the right pane, change Value data from 1 to 3, press OK.
Press OK again to close Install Windows dialog.
Reboot. The installation will continue.