Cannot see the LAN or Workgroup members

Just installed AMD Duron 750mhz machine with 256mb ram to use on LAN in the office of our family business (therefore no qualified IT dept – everyone looks to me :-()
Have installed 13 other PC’s in last 2 years – either as extra or replacements. Noproblems. Cannot get this machine to see anything except itself on Network Neighborhood. Have set identification to the name i have allocated to domain account (on Win Nt4.0 server) have installed TCP/Ip, IPX/SPX, NetBui, have checked cables and hubs, have installed new Netcard but still can only see own computer. Help me please.