Seems that Microsoft has a way to force everyone to update to Windows XP SP2. Below is a quote on how they can do it. If you don't have a valid License... it might be time to install this. ;)
Note 1: All of the above options rely on the presence of a registry key to disable delivery of SP2. This is a new registry key that is used only for the purpose of disabling and re-enabling delivery of SP2. Consequently, there is no additional impact or side effect on the system, and customers will be able to use these options immediately without need for any testing. WU and AU will search for the presence of this registry entry to determine whether or not to download Windows XP SP2. At the end of the 240-day time period, WU and AU will ignore the presence of this registry entry and download Windows XP SP2.
Microsoft and forcing SP2







