[Georgio]

Код:

@ECHO OFF
SETLOCAL ENABLEDELAYEDEXPANSION

SET IN=E:\IN
SET OUT=E:\OUT

FOR %%I IN ("%OUT%/*") DO (
 FOR /F "tokens=2 delims=_" %%J IN ("%%~nI") DO (
  SET VAR=%%J
  IF NOT EXIST "%IN%\*!VAR:~1!*.rar" (
   DEL "%OUT%\*%%J*.rar"
)))