Before you do the reinstall at the minimum download SP2 and an anti-virus program. You could also get a firewall or use the Windows firewall that comes with SP2. Get the install programs and burn them to CD or copy them to an external hard drive if you have one.
Then before you reinstall Windows disconnect from the internet, install Windows and all the drivers you need, install SP2 and the anti-virus, then connect to the internet and go to the Windows update site to get anymore needed updates.
Another option is to get SP3 and there won't many other updates after that. Then reinstall all applications. Here are some sites with details on how to reinstall Windows XP.
http://www.michaelstevenstech.com/cleanxpinstall.html http://www.winsupersite.com/showcase...p_sg_clean.asp http://www.theeldergeek.com/xp_home_..._-_graphic.htm