peer to peer networking help

Hello, I have set up a peer to peer network, working with a mix of xp personal and professorial.

I just set up a common work group named church,

I have all the other computer connected but am have troubel setting up a new dell vistero, It say that its workgroup is church, however when i try to connect to the other work group computer they say ” you do not have permission to assces the church server….” How do i fix this?

Thanks