MS Windows 95 was built on MS DOS, which was culled/modified from QDOS when IBM requested a DOS system from them.

DOS remained at the core of their operating systems until the WinNT kernel became mainstream - namely Windows 2000, which has further spawned WinXP, Vista and now Windows 7 as well as their server products.

It's relevant in the same way that Berkley Software spawned the paths that lead to all BSD based UNIX out there - GNU project included (inspired it at least)... which spawned MINIX and GNU/Linux.

Now, with that nonsense aside, the battleground included Commodore, Apple (with an UI), Amiga (with an UI), IBM, Microsoft and quite a few other players - Digital, WANG, Atari, Tandy, Sinclair and many, many others. During those days, competition was the norm... not so much now.

Back to the so-called subject at hand. Elop as a trojan horse begs to ask one question... how did the board of directors truly fall for the whole "ecosystem" sale pitch from Microsoft and it's not an environment that many people in Europe utilize, support or have shown to be able to access or shown willingness to get behind.

That's like selling fire to people in Hades (note: hyperbole).