Normally when I update a PC with new mb/cpu from a newer generation ( new chipset etc) I re-install windows. Habit I suppose. But I added a hard drive to a system yesterday that unknown to me had a copy of Win 10 on it. Windows created a dual boot and happily booted up from the wrong disk. The main thing here is that the "wrong disk" was from a completely different generation of hardware, yet Win 10 happily just "adjusted" and got on with it. Now this makes me think ~ I am about to update my main gaming PC and it would be a lot easier if I can just replace the mobo/cpu and Win 10 sorts it all out. I think perhaps I am out of date - once upon a time it was pretty lethal to try something like that. Windows could fatally crash or continue to use the wrong drivers. Is it safe these days??