Odd Networking Problem

A small network of 8 computers with mixed OS (4 XP, 2 ME, 1 98SE and 1 2003 Server) and for some reason, all of the computers can see each other and pass information to and from each other. But the computers can not access the 2003 computer. I have allowed the computers to access the 2003 but it says that they do not have permission to access the computer.

Is there a setting that I’m missing? I have gone over and over it and still have not found out what is going on. Any help or suggestions would be apprecated.