>And Windows detected DR-DOS and crashed your computer to kill DR-DOS and MS paid a paltry $150M to Caldera later but they got to upkeep their monopoly in the PC market.
Actually Windows ran perfectly fine over DR-DOS. Perhaps you're thinking of the beta version which included the code to not allow Windows to run on any dos other than MS-DOS. The reason obviously is purely technical. Because of the way Windows 3.1 worked it required access to internal MS-DOS undocumented data structures which could not be guaranteed to work on any other DOS clone.
In fact Windows crashed on MS-DOS 4.0 because the internal data structures changed. MS-DOS 4.0 contains special code for backwards compatibility to trick Windows into thinking its running on the older version.
Actually Windows ran perfectly fine over DR-DOS. Perhaps you're thinking of the beta version which included the code to not allow Windows to run on any dos other than MS-DOS. The reason obviously is purely technical. Because of the way Windows 3.1 worked it required access to internal MS-DOS undocumented data structures which could not be guaranteed to work on any other DOS clone.
In fact Windows crashed on MS-DOS 4.0 because the internal data structures changed. MS-DOS 4.0 contains special code for backwards compatibility to trick Windows into thinking its running on the older version.