Securing Windows XP @ TweakHound
 

This guide will show you how to secure Windows XP. While it covers the basics it also goes beyond them without going into "paranoid" mode...This guide is for home users in a stand-alone or workgroup environment. It is intended as a step-by-step guide and we highly suggest you read through the entire article before taking any action.

http://www.tweakhound.com/xp/security/page_1.htm