This installer contains the GTK dlls with everything they depend on. Theme and theme-engine packages can also be found here, along with an utility to change GTK preferences.
You may need this installer if you happen to run a GTK -based application and need GTK runtime environment to run it. Note that this installer does not include any development libraries or headers. If you want to develop/compile GTK applications for Win32, download the dev packages from Tor Lillqvist's pages (see the Links section).