More on WinXP's product activation
Here is another perspective on Whistler's poison pill written by someone who has used beta 2:
Here's how Activation works. You install Windows XP Professional, Windows XP Personal, or Whistler Server on a system, and it runs without restrictions from the first time that it boots up. But you soon notice a little "balloon" message that pops out of the system tray telling you that you have only 13 days left to "activate" your system. If you click where the message tells you to click, as long as you're connected to the Internet, the system basically comes right back and says, "Thanks, you're activated." No registration, no prying questions.
The article becomes more of a rant but you can find find more here