If you mean, does Vista upgrade check if your Windows XP is legal, then I could not say. If you mean to purchase Vista upgrade, do you need a valid Windows XP license to make it legal: rather rethorical, but I think the answer would obviously be yes. Fact is that I doubt that many people here have a valid Vista (Beta's and RC's excluded). Legally we might be at fault (or are we does evaluating?), but I for 1 will purchase Vista when it comes available in my language (even though it will cost 40% more than US version ), which makes it morally acceptable for me (not legally). Neither. I have legit copy of XP Pro, and am thinking of upgrading to Vista. Just wondering if I will still need to put in XP CD if I made a vlite disc for Vista Upgrade version.