[Bush2000]

What exactly is substantially different? A new hard drive? A new motherboard? Both of which I upgrade during a year. I admit I am not the ordinary user.

Dunno. But in either case, MS is not going to refuse your ability to reactivate. All you have to do is either activate online or call an 800-number -- either automated or operator. No big deal. The point of this exercise is not to prevent you from using the product: It's to make it more difficult for pirates to use the same damn serial number on thousands of machines.

[razorback-bert]

Using MS upgrade advisor:

my scanners, Dazzle, memory card reader and cameras are not compatibile. 26 programs are incompatibile.

I can see an upgrade being quite a pain in the rear for real.