For those having difficulty in running .bat files as export script in windows I would recommend (as an alternative among other possible solutions) to write a simple python script like this:
import os
import sys
nwd=sys.argv[1]
os.chdir(nwd)
os.system('copy index.html index.php')
and make this python script an executable (.exe) file with py2exe as explained here py to exe in windows It worked quite fine in my system (win 7).