Batch script to close all open Command Prompt windows

Be carefull: you might kill more processes than you want:

taskkill /IM cmd.exe

You can add extra filters:

taskkill /IM cmd.exe /FI "WINDOWTITLE eq launcher*"

use

tasklist /FI "imagename eq cmd.exe " /V

to get a glimpse of what cmd.exe processes will be taskkill-ed

You could add the /F parameter to force the process to close but I would only use that if the process doesn't respond to a normal request.