Here is what Microsoft says about service pack 2 .
The latest Service Pack for Windows XP—Service Pack 2 (SP2)—is all about security, and it’s one of the most important service packs ever released. It provides better protection against viruses, hackers, and worms, and includes Windows Firewall, Pop-up Blocker for Internet Explorer, and the new Windows Security Center.
Having personally installed it on several machines without a problem so far I highly recommend it.
Here is even more reasons to put in service pack2 to click here
Plus it has all the service pack 1 security fixes.
It also has a software firewall.
If you want to install it you can go to windows update and follow the instructions, it takes a long time over high speed internet over dial-up it probably takes hours.
Remember if you want me to install this for you can call me 631-321-9313 I have it on disk.. If you find this tip useful sign my guestbook and tell me about it. So if you have dial-up I can install it in less then an hour.