http://en.wikipedia.org/wiki/Graphical_Environment_Manager
If ever there was a good lesson it's this - DRDos was lighyears ahead, and far superior to MSDos. GEM was ridiculously more advanced than Windows, yet they lost. Having the better product doesn't always translate to winning.
Of course things like this helped MS:
http://en.wikipedia.org/wiki/AARD_code
(MS put some code in place to detect DR-DOS and make things not work properly).
"Microsoft Senior Vice President Brad Silverberg later sent another memo, stating: "What the [user] is supposed to do is feel uncomfortable, and when he has bugs, suspect that the problem is DR-DOS and then go out to buy MS-DOS."
It'd be great to see a movie made of this period of time when MS were engaging in so many dirty tricks.