As for me...I did things the easy way when I was first starting with XP Networking...I went with the 10 minute Linux Firewall (there is a tutorial I wrote here on this) using Smoothwall Linux. It took about 20 minutes to install and configure and I had a network setup with VPN...and this is especially good for LAN gaming.
I had a 16 port hub and a WAP. People just plugged in and were on the LAN in less than a minute. If I wanted to transfer files in between XP machines, I used the VPN settings via smoothwall to enable the function and I was secure, fast, and done. Plus, if you ask a smoothwall user via their forums if they've ever been hacked...the answer is always 'NO'...it is one of the best Firewall/VPN clients out there and can run on a spare 150Mhz computer. I'd recommend going that route for ultimate security and configurability.
If you want to check it out, the tutorial is here:
http://daniweb.com/tutorials/14094.html
Hope it helps!