Mc Nealy banned all Microsoft products at Sun, period. It was much more of an emotional decision than a rational one, and all it did was force thousands of employees to go through bureaucratic hell to receive exemptions just so they could get their work done. Yes, I was there, and it was one of Mc Nealy's comically horrible decisions as a CEO (he made many more).
And then, the next step was trying to find a Windows machine... Some employees sometimes had to go to a different building just to fill expense reports.
Good times.