The Network Installation. This method is meant for system administrators. (If installing on a single system, Microsoft will steer you to the Windows Update Website.) If you have several computers to update, it is best to conserve Internet bandwidth by downloading a single (albeit somewhat larger) file and then having all network computers access that file locally. This keeps installation traffic flowing along much larger pipelines than are typically available for remote access.
You can download the Service Pack 2 installation files by clicking the IT Professionals link in the What to Know Before You Download and Install Windows XP Service Pack 2 Web page: http://www.microsoft.com/windowsxp/sp2/sp2_whattoknow.mspx.
Save the service pack executable (it's called WindowsXP-KB835935-SP2-ENU.exe by default) to your computer and then deploy it to network clients as desired.
The CD Installation. Using the CD installation is like installing any other piece of software from a CD-ROM. Just order it from the Microsoft Website (again, you can find a link at http://www.microsoft.com/windowsxp/sp2/sp2_whattoknow.mspx; use the "Get Windows XP SP2" section on the right side). When it arrives, you can pop the CD into the disc drive and then follow the prompts. The installation will look the same as any other, as shown in Figure 1-7.
Figure 1-7. The Service Pack 2 installation process.
Note that this is one CD that Microsoft encourages you share with family and friends.