NTFS and FAT32 dont matter over networks, only local drives (ie: 98 and below can only see FATxx)
In XP you can right click on a folder and goto properties, and there should be something like enable file sharing, then just enable file sharing. Make sure both computers are on the same workgroup, 98 is probably on WORKGROUP, XP might be on MSHOME, right click on my computer, properties, computer name, change (on xp)
then 98 should be able to goto network neigborhood and see the xp's shares. To enable file sharing on 98 you have to right click on network neighborhood, properties, and there should be a button called "file and print sharing" click that and enable em. To share a folder should be about the same as xp.
thats all off the top of my head so you might have to poke around a bit.