eZ publish require at least 256MB ram, that old PC is good for network router, or print server. Try to upgrade. Probadly PHP parser die before send data to web broswer so this is why you have error "page cannot be displayed" or firewall blocks access from remote machines. Also you can check if apache directory is accessable without eZ publish.
Also look here: http://ez.no/community/forum/install_configuration/ez_publish_performance