Cash cows are forever? Hardly. Tell that to buggy whip manufacturers at the advent of the automobile, or more to the point, tell that to IBM's Mainframe Division in 1978. All cash cows will eventually die as they fall out of relevance, and cash cows in the computer industry have a far shorter lifetime than they do in other industries as the computer industry moves far more swiftly.
True, MS's cash cows probably still have a few more decades of life in them yet, but Microsoft is at least smart enough not to rest on their laurels and make an effort at getting into the mobile sector, however pathetic their current attempts at doing so are.
By the way, I looked up United Technologies, and well, I don't know why you bring them up. They're a technology company all right, but they don't look a computer company to me. They look more like Boeing than Microsoft or IBM, and well, the aerospace industry is rather different from the computer industry, and doesn't have anywhere near the same rate of change that the computer industry does.