shared drivers in XP

For all the world, it appears that someone has produced a hack which makes it possible for an outside person to modify files on our harddrive. I found when we run a reg clean, we always, ALWAYS get shared dlls show up.
I read about removing $ signs in appropriate folders for NT, but what about for XP? Total we have about 75 gigs of programs and files at stake, and its not a little thing for some ‘person’ [I use the term lightly] to get into our hard drive from a remote location.