Overview
Windows Desktop Gadgets contains mini-applications or Gadgets which are based on a combination of Script and HTML. They may be used to display information such as the system time and Internet-powered features such as RSS feeds, and to control external applications such as Windows Media Player. Gadgets can run "docked" in the sidebar or they can "float" anywhere on the desktop. It is also possible to run multiple instances of a gadget simultaneously.
Windows Vista ships with eleven gadgets: Calendar, Clock, Contacts, CPU Meter, Currency Conversion, Feed Headlines, Notes, Picture Puzzle, Slide Show, Stocks, and Weather. Several other gadgets available during the Vista beta such as App Launcher, Feed Viewer, Number Puzzle, Recycle Bin and Egg Timer were removed. Windows 7 adds a Media Center gadget and removes the Contacts, Notes and Stocks gadgets. Desktop Gadgets were included in the developer preview and consumer preview of Windows 8, but removed from the Release to Manufacture version. Windows Sidebar is not available on Microsoft Windows Server 2008, 2008 R2, or 2012.
Originally, Microsoft provided a link to a web site called Windows Live Gallery where additional Sidebar gadgets that have been created by third party clients could be downloaded. The site was officially retired on October 1, 2011. Citing security, Microsoft has released a Fixit tool to disable Desktop Gadgets on all operating systems. There also exist tools to install Desktop Gadgets on Windows 8.
Read more about this topic: Windows Desktop Gadgets