You can do a clean install of XP using an Upgrade version of XP...
After formatting your hard drive,install your Upgrade version of XP,just as you as you would the full version. You will then be asked to insert your original CD from your previous operating system to verify that you qualify for an upgrade(see attached image)...end result is a totally clean install of XP.
See this site,
http://www.networkcert.net/xp/install.htm for easy step by step instructions,with screenshots.