Here's a link for enabling your XP Pro installation as a file server. It's not a step-by-step with screenshots, but does discuss what needs to be enabled and why: http://www.practicallynetworked.com/...p_filesharing/
Part of the process in creating a home server is deciding (or explaining to us) what exactly you want to do with this server. Are you wanting to share media such as music and movies with this File Server or just basic word/excel type files? Do you want your server to push applications out to your desktop/laptops? Have you given thought to having your server be your anti-virus manager? Some of these functions/options you may or may not be able to do with Windows XP Pro. One thing you have going for you is that you'll be able to remote into your XP Pro Server via Remote Desktop, which you wouldn't be able to do with Home Edition without a 3rd party app like LogMeIn.
Reason I put that out there is because if you're solely working in a Windows Environment (meaning you don't have much experience with Linux ... if at all) then you may think about purchasing Windows Home Server with some plug-in applications that tailor to your specific needs.
There may be some detractors of this option, but in all fairness, if it's a home server you're wanting that has some cool functions ... Windows Home Server is a pretty good option for your situation. Granted, WHS costs something like $150, but any current OS from Microsoft starts around there now-a-days. Just some food for thought.