[Georgio]

Код:

@echo off
setlocal

for /f "delims=" %%i in ('2^>nul dir/a-d/b "*.avi"') do call:ren "%%i"

endlocal
goto:eof


:ren

 set "old=%~n1"
 set "pref=%old:~13,6%"
 set "pref2=%old:~0,12%"

 ren "%~1" "%pref%_%pref2%%~x1"

 goto:eof