Windows Desktop Gadgets was included in all beta releases of Windows 8 but did not make it to the final release. In Windows 7, Windows Sidebar was renamed Windows Desktop Gadgets, and the sidebar itself was not included in Windows 7. Some reviewers and Macintosh enthusiasts have pointed out the Sidebar's similarities in form and function to Konfabulator (later Yahoo! Widget Engine), which appeared several years previously, and the Dashboard widget engine first included with Apple Inc.'s Mac OS X v10.4, which had been released a few months earlier.

Windows Sidebar was rebuilt and began to appear in Windows Vista builds in the second half of 2005. Windows Sidebar appeared in build 3683 of Windows Vista circa September 2002 and was originally intended to replace the notification area and Quick Launch toolbar in Windows, but these plans were scrapped after the development reset in mid-2004. It included a clock, traffic reports, and IM integration.

Windows Sidebar originated in a Microsoft Research project called Sideshow (not to be confused with Windows SideShow.) It was developed in the summer of 2000, and was used internally at Microsoft.