Home Networking - Permissions

I am trying to set up two desktop PCs in a home network. Both are running Windows XP Pro. One is a PIII and one a PIV. They are both connected to the Internet via a DSL modem and Netgear wireless router. The PIV is connect to the Router via cable, and the other is connected to the Router via wireless adaptor. I have gone thru the microsoft setup procedures and can see the other PC from each other computer. However, when I try to access one PC from the other (i.e. file sharing, etc.) I get a message saying I don't have permission from the Administrator of the other PC to view the files. I am the Administrator on both PCs. Can anyone out there help me figure out how to get the necessary permissions? Thanks in advance for the help.