You should be able to start by having NetBEUI protocol, client for MS networks, and file and printer sharing for MS networks. Both should be in the same workgroup, witrh different computer names. this is the simplest setup possible. Once this works, you can elaborate on it. No hub, eh? Just a crossover cable. Store bought? I have made some crossover cables, and they still don't work as well for me, as a hub.
Probably XP has TCP/Ip as the default protocol. Make NetBEUI the default. that may help. Do it on bothh machines. Both the XP and the 98 machine need it set that way. If NetBEUI doewsn't work, it's probably hardware or drivers (nic)