Changing all files' extensions in a folder with one command on Windows

Question

How can I use the Windows command line to change the extensions of thousands of files to *****.jpg?

Answer 1

In my case I had a directory with 800+ files ending with .StoredProcedure.sql (they were scripted with SSMS).

The solutions posted above didn't work. But I came up with this:

_{(Based on answers to batch programming - get relative path of file)}

@echo off
setlocal enabledelayedexpansion
for %%f in (*) do (
  set B=%%f
  set B=!B:%CD%\=!
  ren "!B!" "!B:.StoredProcedure=!"
)

The above script removes the substring .StoredProcedure from the filename. I'm sure it can be adapted to cover more cases, ask for input and be overall more generic.