Popstar13

did you try disabling the firewall on the server (computer running XP Pro) while trying to connect these last two computers to the network?
Also did you think of reinstalling Network Services with the Windows XP install disc.
if not give it a try go to start > control panel > add or remove programs > Then on the left look for add/remove windows components uncheck network services then recheck it. click next it will rebuild your network files and might ask for O.S. install disc. Then reboot computer and retry connecting to network....
post back with update, see where your at with this problem...