I would recommend you uninstall (not just disable) Zone Alarm till you get this sorted. The fact that you can't ping one of the 98 boxes from the XP box is strongly suggesting that ZA is blocking it. You also might consider installing NetBEUI as a test and workaround. In 98 it's simple, just add protocol. With XP, it's a bit more involved.
http://support.microsoft.com/default...b;en-us;301041