There used to be a command Minimize All windows (Win+M) up to Windows 2000 but it was removed in XP and replaced with "Show the desktop". But the keyboard shortcut (Win+M) still works. And after doing Win+M, the taskbar context menu shows "Undo minimize all windows" (Shift+Win+M).

For mouse users, is it possible to put "Minimize all windows" back next to "Show the desktop" via Taskbar Context Menu Tweaker? :)