Rename multi files in a folder on Windows.

@echo off

set count=1
set basedir=C:\old_data\report
for /f "tokens=*" %%G in ('dir /a-d /b %basedir%') do (call :subroutine %%G)
goto :eof

:subroutine
for /F "delims=_" %%a in ("%1") do (
   ren "%basedir%\%1" "%%a_SPRW_Light_%count%.txt"
)
set /a count+=1
goto :eof

Example:
"20141013_Test_Rept.dat" will be renamed to "20141013_SPRW_Light_1.txt"