I dont have much experience with Home... but here goes.
I assume you have 2 Windows XP Home PC's, connected via RJ45 cables to a Network Hub, Switch, or Router.
Assuming you are using a router and not a switch, and that it is handing out DHCP ip addresses to the clients.
Make sure that you have Simple File Sharing enabled on your computers. Then share a folder, assigning any security restrictions you need.
Let me know if you have done all of that, or if the setup varies from what I listed.