@echo off
  setlocal
  for /r %1 %%D in (* .) do call :lowercase %%~D
  endlocal
  echo  Done.
goto :EOF


:lowercase
  set F=%~nx1
  set F=%F:A=a%
  set F=%F:B=b%
  set F=%F:C=c%
  set F=%F:D=d%
  set F=%F:E=e%
  set F=%F:F=f%
  set F=%F:G=g%
  set F=%F:H=h%
  set F=%F:I=i%
  set F=%F:J=j%
  set F=%F:K=k%
  set F=%F:L=l%
  set F=%F:M=m%
  set F=%F:N=n%
  set F=%F:O=o%
  set F=%F:P=p%
  set F=%F:Q=q%
  set F=%F:R=r%
  set F=%F:S=s%
  set F=%F:T=t%
  set F=%F:U=u%
  set F=%F:V=v%
  set F=%F:W=w%
  set F=%F:X=x%
  set F=%F:Y=y%
  set F=%F:Z=z%

  if not {%F%}=={%~nx1} echo %~p1%F%&ren %~pnx1 %F%
goto :EOF