Need Password to access

I have a very simple network. Two computers, both running XP Pro. A simple 5 port network hub. DSL coming in and two computers connected. Both computers access the DSL no problem. I can access the files on my son’s computer but when I try to access my files from his computer or use my printer from his computer it asks for a user name and password which I never assigned. Very frustrating. I used the simple network wizard on both computers but I must have done something wrong since I cannot access my computer from his. Help!