The default installer for Window Clippings 3 requires an Internet connection. This can sometimes fail if your Internet connection is very restrictive (proxy servers, firewalls, etc). As an alternative you can download the complete installer for an offline installation here:
http://windowclippings.com/download/offline
This will download a ZIP file that contains the Windows Installer package (WindowClippings.msi) that you can then copy to your desktop and run without requiring an Internet connection.
Kenny Kerr 
I would love to learn more about the licensing internals of Window Clippings to use in our own product(s). Very fast and easy.