Microsoft became successful primarily by IT department mandate in the 80's and 90's. Apple has been successful due to its focus on user/consumer experience. We now live in an era where consumers have a larger voice in technology selection and the Microsoft/Corporate IT department mandate is becoming less significant. You can beat Apple only by delivering the best consumer experience possible.
From what I read, I think there were not that much IT departments in the 80's outside technical companies, I think Microsoft got its position because of a series of factors, one of them was the presence of Visicalc-like programs (specially Lotus 1+2+3), in the 80s Apple was already offering an absurdly good user experience compared with Microsoft, yet it failed in the first time.
I remember that people got pretty excited with Windows 95, I don't think that this excitement was a enterprise mandate at all.
