@ECHO OFF
FOR /R %%F IN (*.flac) DO CALL :ProcessFile "%%F"
GOTO :EOF

:ProcessFile
CD "%~p1"
REN %1 %~n1%~x1~old
C:\PROGRA~1\FLAC\FLAC --delete-input-file -o %~n1%~x1 --compression-level-7 "%~1~old"
GOTO :EOF