Errm Karlos, are you sure he didn't mean "taking on Windows" as in making an os that is competitive with Windows like Apple did
They did? Last time I checked, there were vastly more Windows installations out there than OSX ones, totalling around 85% of the "web client" market share*. Might have something to do with the fact that Windows, for all it's many sins, isn't tied to a single hardware vendor.
*this is basically a measurement based on browser user agent strings, which isn't that reliable due to spoofing (and other issues), but should be roughly ball-park. If anything, the figure is likely to be higher since many business PCs running windows are operating behind strict firewall rules that limit their access or are blocked from accessing the internet all together.