Gnome

I have ruby 2.0.0
Im installing this ruby-gnome2-0.16.0-1-i386-mswin32.exe (12.3 MB) which I found here:
http://sourceforge.net/projects/ruby-gnome2/files/ruby-gnome2/ruby-gnome2-2.0.2/
I install it to the C:\Ruby200 folder

I try the following code, saved in a file called base.rb
require 'gtk2'
window = Gtk::Window.new
window.show
Gtk.main

When I run it with my start command prompt with ruby: ruby base.rb
I get the error that in require, cannot load such file gtk2 (Load error)

What am I doing wrong?