set n=1

:starline

for %%j in (*.txt) do (

:3

if exist D:\work\test\new_%n%.txt (set /a n+=1&goto 3)

set file=%n%.txt

for /f "skip=1 delims=" %%i in ('type "%file%"') do (

echo %%i >>D:\work\test\new_%n%.txt

)

set /a n+=1&goto starline

)

::start "" D:\work\test\new_%n%.txt

::pause>nul

@echo off

for /f "delims=" %%a in ('dir/b *.txt') do (

type "%%a">>All.txt

)