I have several Xp machines here at home and I have them all set up on a small network connection. As long as they are all listed on the same domain name, i.e. "my home network", you should be able to access files across each machine as I do. You can set up priveliges for each user or have everyone with admin abilities. Xp has a network set-up wizard in the network connection window.
oops - forgot to say that this sets up a network bridge from machine to machine. so a seperate network connection will be enabled - one for your regular network (broadband, adsl, etc) (if applicable), and one for the network bridge.