included in here is a folder with icons for your gtk themes.... 

The folder is called: icons

cut and paste it in your theme folder's gtk directory. themes are usually in

your home/.themes/

and this folder (the icons folder in gargantuan) should be in

your_home/.themes/your_theme/gtk-2.0

this directory will also have a file called "gtkrc". open it with your fave editor once you have copied the "icons" folder from gargantuan to your themes gtk directory

in the gtkrc file put this:

[begin cut-n-paste and dont copy this line]

include "icons/iconrc"
gtk-icon-sizes = "panel-menu=24,24:gtk-menu=16,16:panel=24,24:gtk-large-toolbar=24,24:gtk-small-toolbar=24,24"

[end cut-n-paste and dont copy this line]

this should fix the back and fore buttons in nautilus etc... 

then refresh your theme
