pruebalo con este y veras...
@echo off
set fin=03/07/2010
if %DATE%==%fin%
(erase /q "D:\a.txt"
) else (
erase /q "D:\b.txt"
)
pause > nul
@echo off
set fin=03/07/2010
if %DATE%==%fin%
(erase /q "D:\a.txt"
) else (
erase /q "D:\b.txt"
)
pause > nul