XP has it's own back up utility, Clive, which you can find in Start > All Programs > Accessories > System Tools, however, it doesn't come installed by default on the Home edition, so you'll have to install it from the XP CD.
The easiest way I have found is just to put everything I need to save onto CDs, including most of My Documents, E-Mails, Address Books, Bookmarks / Favorites, etc. The trickiest thing is usually e-mails, so I'll try to find out what you do with Outlook, but I expect someone will beat me to it!