Microsoft's Windows Desktop Update was an optional feature included with Internet Explorer 4, which introduced several updated shell features to the Windows 95 and Windows NT 4.0 operating systems. These features became part of the standard installation in Windows 98 and later versions. It included features such as Active Desktop and tight IE4 integration ^{[citation needed]} with the Windows Explorer. It was downloadable as part of IE4 for all versions of Windows 95 except Windows 95 OEM Service Release 2.5 (4.00.950C) which included IE4 (but not slipstreamed) and installed it after Windows 95 was set up. It was also available as part of IE4 for Windows NT 4.0. It was not included in any later version of Internet Explorer (IE5 onwards) although if the Windows Desktop Update was installed as part of IE4, Internet Explorer 5.0 or 5.5 updated some of the shell features such as sorting by name in a context menu and drop down menus whenever menus or toolbar buttons did not fit on the screen.

Updates to the Windows Desktop Update were part of IE 4 hotfixes and service packs. Later, shell security updates for Windows 95 and Windows NT 4.0 included both the update to the Windows Desktop Update version and the original version. Also sometimes the Windows Desktop Update version and the update to the original version were packaged separately.

The Windows Desktop Update also added the ability to create desk-bands like the quicklaunch bar. It also updated the Windows file manager, explorer.exe (also a shell), to be more modular and extensible.

• http://wallabyweb.com/training/IE4/ Detailed technical documentation of Internet Explorer 4.0, including Windows Desktop Update
• http://www.petri.co.il/install_active_desktop_on_nt_40.htm Detailed HowTo about the installation of the Windows Desktop Update with IE5 and IE6