Microsoft has killed gadgets.
The above link points to this statement:
Because we want to focus on the exciting possibilities of the newest version of Windows, the Windows website no longer hosts the gadget gallery.
Gadgets installed from untrusted sources can harm your computer and can access your computer's files, show you objectionable content, or change their behavior at any time. If you are concerned about the safety of gadgets you’ve downloaded in the past, you can learn more about gadgets and steps you can take to protect your PC.
Some info for developers: