Google Gadget Designer 1.1 application for Windows, you can easily create a Desktop gadget from scratch. Gadget Designer is also useful for modifying existing gadgets, such as when you need to change a gadget's user interface or repackage a gadget.
This Google official tutorial leads you through the process of creating a simple Google gadget.
Step 1: Download and Install Software
Step 2: Create a New Gadget
Step 3: Add a UI Element
Step 4: Add Event Handling
Step 5: Get Debugging Output
Step 6: Customize Strings and Settings
Step 7: Package the Gadget
What to Do Next