Did you install Netbui on all the computers? You would have to.
I would forget about Netbui and install them all using Netbios.
For each computer make certain:
. They have the same workgroup name
. They have unique computer names
. That under TCP/IP properties, Netbios over TCP/IP is enabled and bound to the network adapter.
. Remove any unneeded adapters
. Remove any unneeded protocols: IPX/SPC, Netbui, etc.
. Windows for Microsoft Networking installed
. File and Printer Sharing Installed
. Windows Logon selected
. There is a username and password assigned on each machine to logon
. That the XP machine have all the username/password entries for the network made, or the Guest account is enabled
. Every machine shares something, printer, file or folder
. Every machine login is done with a password, the Enter key or Okay, and never the Escape key or Cancel.