I run a router only with no firewall. Also, adding a user ID is something I've tried. I can't recall if I've run the network setup dealie or not. Maybe I'll try that. Still, do things have to be this convoluted just to get a simple home network fully functional? To your first point about...
I actually have the opposite problem. Though I have only three machines total, one of which is running Windows 7, both of my XP machines cannot access the main drive on the Windows 7 machine, though my Windows 7 machine can access everything on my XP machines. My workgroup name is the same...