How to fix missing Windows-brought EXE files (primarily for CMD) such as missing SETX.exe

The issue context:

I want to use SETX to set system variables in CMD. But my computer seems to be missing this file, and I didn't find it.

Workaround:

To enter commands in CMD:

Sfc/scannow (Note that SFC has a space, and must run CMD under administrator privileges, the operation goes from http://www.fixerrorkit.com/fix-error/fix-setx.exe-error.html)

Extended:

SFC (System file check): Detects files protected under Windows and replaces them directly with the correct version if they are missing or incorrect. (Detailed explanation: http://ss64.com/nt/sfc.html)

How to fix missing Windows-brought EXE files (primarily for CMD) such as missing SETX.exe