Photoshop CS // default brush set

F:\Program Files\Adobe\Photoshop CS\Required\Default Brushes.abr

This, I would guess, is the path to Photoshop's default brush set - meaning the one that gets loaded each time you reset your brushes.

My question is, is it safe to mess with this? I mean, is it safe to say, add some brushes to that set, or delete some, or maybe even replace it with an entirely different set?

I just don't want to screw up anything. Have any of you tried to do something with PS's defaults?