This is a little warning from a friend who downloaded XP's Service Pack #2

I couldn't wait to get it and installed the program after briefly skimming Microsoft's instructions. I should have dug a lot deeper!
Immediately after installation a pop-up window appeared saying my computer was unprotected and I should turn on the Windows firewall which I instantly did. Big mistake.
It wrecked havoc with my Norton and created general chaos even after I turned the firewall back off. I concluded the only recourse was to uninstall it which created even more problems until Windows declared that it had to shut itself down to prevent further damage to my computer. Then of course you have zero access to any of the sites that might tell you how to fix the problems. I'm back up now but it was a harrowing experience that I wouldn't want anyone else to "enjoy".
Be sure you read Norton's instructions too and understand them thoroughly before installing SP2.

I am now advised to wait awhile before trying again as they definitely need to get some of the kinks cleared up.