This first version of Windows, which was released in 1985, ran a program known as Microsoft Executive.
Many believe that Windows 1.0 was an inferior product to many others at the time, some considered it unusuable. The best GUI for the PC platform at the time, many maintain, was GEM. Another alternative was Desqview/X, which is still viable as an X server on a DOS machine. Windows 1.0 was superseded in 1987 with the release of Windows 2.0.
See also History of Microsoft Windows.