Make sure win98 has something shared, ie its HDD. Also, sometimes the network wizard and network neighborhood is a bitch. Try typing in the address box something like this
...and if that doesn't work
Make sure NetBIOS is installed. Even though you can do File Sharing through TCP/IP NetBIOS is a whole lot better.
Another possibility that may work is set the WinXP Box to be the DHCP server, and auto assign the IP for the 98 Box.
I think the NIC on the 98 box might be screwed, i installed win 2k on both and still, the laptop see's both but only can connect to itself, and my comp can only see itself, tomorrow i shall attempt a different NIC, but rite now it's new years, and i've had too much to drink.