@chb: Well, PCs still do stop working eventually, so they do have to be replaced. But with more and more PC components being consolidated into SoCs or built into motherboards, there are fewer and fewer things to go bad. I think PCs simply last longer nowadays.
If this was the case Apple would definitely be in trouble. Everything from their iPhones to their Macbooks have a reputation for being durable. There are loads of people still using iPhone 3's and iPad 1's because they last a long time.
Laptops which most people use are more susceptible to being replaced for broken power supply points, dead batteries and the thrashing they tend to get from mobile use.
It is a shame this thread has attracted nonconstructive anti-ms haters, but the financial implications of 10-15% of millions (if not tens of millions) of licenses is not something to cross your fingers and hope for the best for.
It is the repositioning of Microsoft with regard to their userbase and financial model, dressed as "Windows re-imagined" that in my view marks the start of the demise of Microsoft. No company in history has done what they have attempted to do in the last year and lived long enough to regain their market dominance.