Make a new icon using photoshop and this :

Go into reshack and replace the icon using the icon you build in ico workshop.
when you're building icons make sure to make all the different sizes.
I made an icon for my own use, which includes sizes up to 128x128 and 256x256 << Mac
128x128 is for vista/win7 desktops to show a bigger icon.
Also, make sure you include the different color types, cause if someone has lowered their color settings your icon will look retarded.