Not to mention how Chicago (codename for Win95) was delayed and how MS was attacking OS/2 in the meantime (look up "Microsoft Munchkins" for one example). And it helped continue MS's legal troubles with Digital Research/Novell over DR-DOS. In contrast, OS/2 did not run on top of DOS at all, and DR-DOS 5.0 was released not long before Win3.0 was released. And MS released the OS/2 2.0 SDK to developers at the end of 1989. Yea, I am talking about the JDA break-up circa 1991. The MS-IBM JDA was not perfect, but the alternative MS chose was a lot worse and delayed native 32-bit programming by years (Intel released the 80386 in 1985!).