In reply to summo:
> I think Microsoft have realised it's possibly cheaper to give away W10, than to keep paying people to patch up older versions.
If that were true, there would be no deadline to upgrade. Unless their plan is to simply keep extending the deadline, and the 'deadline' is just a way to encourage people to upgrade sooner/increase takeup.
Living up to my online moniker, I suspect something more underhand is the real cause, and that Win10 provides them with alternative revenue streams (by data exploitation). "You don't get owt for nowt" comes to mind.
Which brings me to the question: "just how new is the Win10 codebase, compared to XP/Vista/2k/7/8, and what new features has it added?"
If it's a matter of patching an old, creaking codebase, or moving on to a bright, shiny new codebase (riddled with as yet undiscovered bugs), then I might accept the premiss of the patch cost. But I suspect that honking great swathes of code are re-used. In which case, what substantive changes actually occur with a 'new release' of an OS? Or is it just smoke and mirrors; "Malibu Stacy, with a new hat"?