I agree with Usil. The only time I tried--out of professional curiosity, mind you, not malicious intent--I got the invalid product key response; but I do know of people who have done it. There was a 120-day period at one time, but I don't know what's up with that now. I think M$ created a policy before they had the means to enforce it which is what started all the confusion. That's why I think they've gone out of their way to announce their policy before Vista is even available, to eliminate the confusion this time around.