You don't actually need both protocols. NetBeui is more secure for sharing and not accessable from outside. You can bind NetBeui just to file and print sharing. But TCP/IP will work for both.
The Components needed;
1. Client
2. Protocol-TCP/IP or NetBuei
3. IP addressing and subnet mask
4. Workgroup
5. Shares/Permissions
6. Users login and password
More than likely the problem you're having is that you haven't added the 98 users on XP.
So if win98 station one logs in as "station1" with a password of "letmein" that user with the same password must be added to the users list for the XP system.
A Firewall may be blocking network traffic. Windows XP comes with a builtin firewall that can be disabled in the properties of the network connection. If you use a software firewall you'll need to change the settings as directed by the instructions provided with the program. Disconnect from the internet then disable any firewall to see if that's the problem. Before reconnecting to the internet find out how to allow the workgroup traffic and still block others.
If you have a highspeed connection and your network is setup using DHCP then more than likely the cable/DSL modem or router is providing firewall services and may also be blocking the internal connnections. You may need to go into the settings and allow for your local network traffic to pass. Use the instructions that came with your unit.