Just make sure you back up all your data, favorites, email, etc.
Also, you may want to go into the Device Manager and write down the
components you have installed. The most important ones are:
modem
network adapter
sound card
video card
Before installing XP Home, you might want to download the newest drivers for
each device and put them on a CD so you have them after installation. I can
tell you from experience that it will be a real pain trying to find
everything after the fact. The manufacturer's CDs might not cut it. If the
device is older, the XP drivers may not be on the CD that you got with the
device or PC.