1. Create a new directory <newdir>
2. Run the following command (you can replace newdir with the your directory name and some_prefix with your prefix the same applicable for extension as well. My eg., rename only the png files of the directory (there were no other extensions available).
i=0; for x in *.png; do cp \"$x\" "newdir/some_prefix_$i.png"; i=$(($i+1)); done
Windows should have supported bash scripts natively. OSX is handy only because they inherited from unix.