It's been a while (2-3yrs) since I've done a 98 machine, its not that much different than XP, the names are different.
In the control panels there is one called Network. This is were the TCP/IP setting are at, and where you can start file sharing up if needed. Set the Computer Name, and Work Group. If in the same group it should be easy to find.
start> run> winipcfg? is the program to check and see what setting were pulled from your router. You can issue release and updates on your ports. If you change something will out rebooting.
There should be a shortcut to My Network Neighbor. This is were you can search for you XP computers.