A variant using Bat/Powershell (need .net framework):
replace.bat :
@echo off
call:DoReplace "Findstr" "replacestr" test.txt test1.txt
exit /b
:DoReplace
echo ^(Get-Content "%3"^) ^| ForEach-Object { $_ -replace %1, %2 } ^| Set-Content %4>Rep.ps1
Powershell.exe -executionpolicy ByPass -File Rep.ps1
if exist Rep.ps1 del Rep.ps1
echo Done
pause