Windows XP Updates Legit Vs Not-Legit

DumNDuMMer

Here's the deal: I have 5 machines (1) laptop and (4) desktops. 2 of the desktops have their own "Genuine" OS which would be XP Home Edition, the other 2 desktops and the laptop have XP Professional SP2 installed "the not so Genuine OS" but the thing is that I can get Windows Updates without a problem for the XP Pro Installs. It's not like those cracks/patches I've heard about where you have to keep replacing/updating certain files to keep getting Windows Updates every now and then. For what I understand, if it let's you download Windows Updates without a problem, then it's legit? or just another crack? "GOD" let me borrow his "install" disc to install an OS on 3 machines and make sure they work. It's not guilt what I have now, it's more like wondering, how can this be so? The same key, the same disc, it let's you get Windows updates & downloads. Wouldn't have Microsoft done something regarding stuff like this? I ask because this is not the first time I've installed "non-legit" operating systems on a machine. In other times, if you do not activate Windows, it stops working properly until you purchase a "legit" key or just doesn't let you get Windows Updates if it doesn't ask you to activate. What I'm wondering is if I could possibly run into this problem later on down the road with the 3 machines that have XP Pro installed on them?
I say "the best things in life are free" and so far so good, but in this situation, the question is for how long?