XP also automaticly detects network shared folders. IIRC, it already has one by default, but you can share whatever folder manually.
Not to mention network drive mapping, which, while a bit harder to setup, give much more options than just standard folder sharing.
Of course, that’s also not mentioning anything you could add on top of the OS (FTP servers, samba, SSH servers for SFTP, …)
As for the computers being close, I have a 50 metre RJ45 cable connected to my internet modem.
Of course, you can get straight cables up to insane length, but I really don’t think you can get crossover cables that lenghty (there’s no real market for those).