This package can be installed as a regular R package.
In other words, the command 
   R CMD INSTALL RGtk2

On Windows, the user should set the environment variable GTK_PATH to the 
location of the root directory of the GTK distribution (ie c:\GTK).

The binary version of this package for Windows can simply be installed
using the Windows R GUI.

In all cases (i.e. Unix or Windows, source or binary), you will need
to have the appropriate Gtk libraries.

For Windows, you can download the GTK Developer's Pack
from 
   http://gladewin32.sourceforge.net/

For Unix, you can fetch the source files for the different
libraries from
   ftp://ftp.gtk.org/pub/gtk/v2.8/

GTK makes extensive use of other libraries
and particular versions of these dependant libraries.  As a result,
installing GTK (under Unix) can be a time consuming and apparently indirect
process that involves installing numerous sub-libraries.