Networking problem. i had a problem with my network..i had 5 workstation and 1 server all of them

Question

i had a problem with my network..i had 5 workstation and 1 server all of them are running on windows xp..my problem is i can only ping 3 of my workstation and other 2 are not..and all of my workstation cannot ping the server..other of my workstation can only ping 2 in peer to peer communication.