I have done this, but it was a long time ago. I may be wrong but double check the following:
1) Your 98 PC has to be set to logon using one of the networking services (Microsoft Windows logon, I think) & make sure the password you use in the logon box is the same of that on your XP machines.
2) Install IPX/SPX protocol on your XP machines.
3) Make sure all your files/printers are set to share & that the relevant folders on your hard drives are shared.
4) You may also need to set up permissions on the XP machines, to allow the 98 machine access.
As I say it has been a while since I have done this, so I may be totally off the mark in which case somebody else in here will be able to help you out, but the above is worth checking! Good luck.