@echo off&setlocal enabledelayedexpansion
for /r %%a in (*) do (
set "str="&set "var="&call :lp "%%~na"
if defined var ren "%%a" "!var:~1!%%~xa"
)
goto :eof
:lp
if not defined str set "str=%~1"
for /f "tokens=1* delims=(" %%a in ("%str%") do (
if "%%b" neq "" set "var=%var%(%%a"&set "str=%%b"&goto lp
)