Create an HTML page that does something interesting.
Create the XML file for the gadget manifest.
Test the gadget with Sidebar.
Steps
Open the Sidebar.
Click the Start button, then click on All Programs. The Sidebar can be found under
the "Accessories" folder.
in taskbar, find icon
Locate your gadgets folder.
In a "Run" prompt from the Start menu (Windows Key+R), type
%userprofile%\AppData\Local\Microsoft\Windows Sidebar\Gadgets
Your Gadgets folder(hidden folder) will now open. It will be something similar to:
c:\Users\YourUsername\AppData\Local\Microsoft\Windows Sidebar\Gadgets
Create the gadget folder.
Create a folder called HelloWorld.gadget inside the Gadgets folder.
Gadgets must be a folder whose name ends in .gadget for Sidebar to recognize the
gadget.
Create the gadget folder.
Use something capable of creating an HTML text file, such as Notepad.
The HTML file should contain the following content.
HelloWorld.html