Slow TCP/IP connection

I a small network running WINNT4.0 Server with Win98 Workstations. I have one Workstation that has a very slow connection to the server as well as all the shared resorces on the Network. all the Workstations have the same 2 protocals installed, TCP/IP and NetBEUI. This machine is very slow on bothe the TCP/IP ( downloading files from the Web) and accessing files from the local network. I have changed the NIC and checked the wiring. what could be slowing this machine down?