Hello JT2, to network the two machines for simple file transfer should be fairly straightforward.
First things first, plug the cable into each machine, the cable you use must be a crossover type and not a straight through type.
Next you need to open up the control panel on the xp machine and choose icon 'network setup wizard' and follow the instructions.
Next is the 98 machine, the following click here should give clear instructions on setting this side of it up.
Bear in mind that any firewalls on any machine will need configured to allow communication between the two pc's. If your not sure how to do this, disable your firewall whilst your also disconnected from the net. This will allow you to see that the network is working properly without the firewall hindering progress, once up and running, you can re-enable the firewall and configure.