Windows 1.04 is a minor update to Windows 1.0, released on 8 April 1987, about six months before Windows 2.0. It included some minor changes and bug fixes, support for IBM's new PS/2 line of computers (though PS/2 mouse and VGA display drivers only shipped with IBM's OEM release), as well as an updated boot screen with Microsoft's new logo from 1987. Like versions 1.02 and 1.03 before it, it was available in multiple languages.

This also appears to be the first retail release to be shipped on 3.5" floppies in addition to 5.25" ones. Calculator, Control Panel, and Reversi have been updated to 1.04. Spooler doesn't show what port the printer isn't connected to anymore.