[megaloman]

Код:

@Echo Off &Cls
	Set "BoxIn=Z:\Box_Arc"
	Set "Mask=*.jpg"
	Set "Ex=_m\.jpg$"

	If Not Exist "%BoxIn%\%Mask%" (Echo Files "%BoxIn%\%Mask%" not found &Pause &Exit /B 2)

	For /F "usebackq delims=" %%i In (`2^>nul Dir /B /A:-D "%BoxIn%\%Mask%" ^|FindStr /I /R /V /C:"%Ex%"`) Do Ren "%BoxIn%\%%i" "%%~ni_m%%~xi"
Pause
Exit /B