XP SP2: Download and Save For Installation on Multiple Computers
This explains where to download the large version of SP2 for installation on multiple systems.
This is not the version you want if you installing SP2 for one computer. A much smaller version will be available soon enough.
If you need to download everything and burn it on a CD for multiple installations, this is the download for you.
Windows XP Service Pack 2 Network Installation Package for IT Professionals and Developers





