Yes it is true. You can build your own gadgets for Windows Vista and can have them displayed in the Sidebar, all you need is a little knowledge of HTML and XML and that would be all.
In simple terms a gadget is a HTML or XML file is displayed in the sidebar and is intended to display you some information from your computer or from the internet. In this article we will let you know how to create your own gadget.
A gadget consists of a main XML file which has all the important information about the gadget and has link to the HTML file which works on it. The XML file contains information like the gadget name, author name, Website URL, Description, Icon Source information, Link to the HTML file etc. To have a look to any existing gadget’s XML file just rename the extension of the gadget to .zip and unzip its contents. You will then be able to see the XML files and the main HTML file. This can be used as the base for your Gadget.