[sov44]

angel_lyucifer, пробуйте

Код:

@echo off
setlocal EnableDelayedExpansion

set filename=old.txt
set $filename=new.txt

set in=#sound_on_vlp
set out=#sound_off_vlp

for /f "tokens=1* delims=]" %%A in ('find /v /n "" ^<"%filename%"') do (
	set line=%%B
	if "!line!"=="%in%" (echo %out%>>%$filename%) else (echo.!line!>>%$filename%)
		)
del /q %filename%
ren "%$filename%" "%filename%"
	
exit /b