Windows Genuine Advantage

hi all

recently i read an article in techrepublic blogs ( http://blogs.techrepublic.com.com/window-on-windows/?p=672 )about the ability to make your Windows XP genuine by changing any the key.

i have installed windows xp from pirate CD into Dell PCs, after that i changed their Windows Key to one which is fixed on their case (proof of license). after that i update these windows XP successfully, finally i received a message from windows told me that my windows is not genuine.

what is the wrong in my story

note: i have asked the same question but i did not get convincing answer
https://www.techrepublic.com.com/5208-6230-0.html?forumID=101&threadID=267075&messageID=2529463

thank you all