Windows Desktop Update was an optional feature by Microsoft that was included with Internet Explorer 4 (IE4, released in September 1997), which introduced several updated shell features to the Windows 95 and Windows NT 4.0 operating systems. These features later became part of the standard installation in their successors, which were Windows 98 and Windows 2000, respectively.
The Windows Desktop Update included features such as Active Desktop and tight IE4 integration with the Windows Explorer. It was downloadable as part of IE4 for all versions of Windows 95 except for Windows 95 OEM Service Release 2.5 (4.00.950C), which included a standalone version of IE 4.0 plus the Windows Desktop Update (but not slipstreamed) where it was automatically installed after the standard Windows 95 set-up. Similarly, the shell update was also made available as part of IE 4.0 for Windows NT 4.0 (with Service Pack 3 or later).
While the Windows Desktop Update was officially only an optional user component under Internet Explorer 4.0 releases and was not formally included in later versions of Internet Explorer, users can extract the Windows Desktop Update installer from the IE4 setup files using standard .CAB extraction tools or use IEAK to generate a version of the IE 5.0x, 5.5 or 6.0 setup which included the update. Also, command line parameters or edits to a temporary configuration file can be used to instruct installer of those versions of IE to install the Desktop Update.
For example, in the case of IE 5.0x and 5.5, the IE5 setup will install some new shell features if the Windows Desktop Update is installed, such as sorting by name in a context menu and drop down/overflow menu buttons whenever menus or toolbar buttons did not fit in the Explorer window on the screen.