The issue has been resolved, and it involved changes to the Daniel XP box.
The 'Daniel' computer used by Daniel used to be Tom's (my children get my old computers). Although the computer name and user name were changed to reflect the trickle-down, I now wondered if the changes went deep enough.
So a new user account was created on Daniel. After declining the automatic "Take a tour of Windows XP", I double-clicked on the Tom icon in network settings, and it finally asked me for a username/password.
Daniel now has access to all Tom's resources.
Thanks, all, for your help.