sentences:  Between the Caldera-owned DR-DOS and competition from IBM's PC DOS 6.3, Microsoft moved to make it impossible to use or buy the subsequent Windows version, Windows 95, with any DOS product other than their own.Claimed by them to be a purely technical change, this was later to be the subject of a major lawsuit brought in Salt Lake City by Caldera with the help of the Canopy Group.Microsoft lawyers tried repeatedly to have the case dismissed but without success.