Notepad won't launch, doesn't show in task manager

Today I tried to launch Notepad and nothing appeared to happen -- no error, nothing in the taskbar. I checked Task Manager and the Detail tab shows no entry for notepad.exe.

There are two notepad.exe binaries, one in C:\Windows and one in C:\Windows\system32. Both show the same behavior (not launching), and both have a SHA256 sum of CA2837031952C32BC1639A416F5C2ADCEEBF33507D216E554A3B47B17C52E9B1. It's interesting that the file was updated on 10 Sept, but the checksum is the same on another system where Notepad works fine.

sfc /scannow showed an error, so I ran DISM /Online /Cleanup-Image /RestoreHealth. This failed with 0x800f081f, The source files could not be found, so per this page I ran Dism.exe /online /Cleanup-Image /StartComponentCleanup which reported success. I ran DISM /Online /Cleanup-Image /RestoreHealth (success) and sfc /scannow (success), but notepad still won't run.

I deleted Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Notepad, still won't run; rebooted, still won't run.

I rebooted in Safe Mode, won't run; sfc /scannow again, won't run.

I haven't identified any other programs that won't run (Wordpad is fine, for example) and recent Defender scans come back clean.

sfc /scannow showed an error, so I ran DISM /Online /Cleanup-Image /RestoreHealth. This failed with 0x800f081f, The source files could not be found. I have tried typing "notepad" in the Start menu and clicking the result.

Something is badly broken. DISM and SFC should both run and correct errors and Notepad will start from either Start Menu or Task Manager.

It is now time to run a Windows 10 Repair Install

Go to the Media Creation Link:

https://www.microsoft.com/en-us/software-download/windows10

Windows 10 is running, so click on the Download button (not Upgrade Button) and select Run.

This will launch the Repair and proceed normally.

Start with the option to Keep Everything.

Notes for Repair Install:

1. This process will upgrade all applicable drivers.
2. This process will make you uninstall incompatible software
3. This process will not fix damaged User Profiles. Must use Keep Nothing