Windows symbolic link, save some space.

Windows Vista and 7 introduced "symbolic links" (something *nix systems have had for a long, long time) which basically allows you to create links to files. They act like shortcuts, except programs will treat them as the full file. A good usage of symlinks is when you have multiple copies of the same game. You don't need to copy the entire data, just only parts of it.

set maindir="D:\Installed\Call of Duty\main"
set targetDir="C:\Users\simplythebest\Desktop\CoD\main"

MKLINK %targetDir%\pak0.pk3 %maindir%\pak0.pk3
MKLINK %targetDir%\pak1.pk3 %maindir%\pak1.pk3
MKLINK %targetDir%\pak2.pk3 %maindir%\pak2.pk3
MKLINK %targetDir%\pak3.pk3 %maindir%\pak3.pk3
MKLINK %targetDir%\pak4.pk3 %maindir%\pak4.pk3
MKLINK %targetDir%\pak5.pk3 %maindir%\pak5.pk3
MKLINK %targetDir%\localized_english_pak0.pk3 %maindir%\localized_english_pak0.pk3
MKLINK %targetDir%\localized_english_pak1.pk3 %maindir%\localized_english_pak1.pk3

Example is implemented on call of duty but you can play around to save huge space where you wish to have multiple copies of same data/file/games. :)