To start with, make sure your XP firewall is TURNED OFF. This is only a temporary measure until you have successfully configured the network.
Each computer must be on the SAME Workgroup. You can call this what you like, providing it remains consistent on all machines. Confusingly, the Default is; Workgroup!
Each computer must have a UNIQUE name, Bill and Ben for example, but again, you can call them whatever you like.
click here for a good resource, to read about setting up your network with step by step "How To's".