nt/9x lan 10/100 nic

My network in pc’s is not able to ping server(win NT).
I am only able to ping the server in one case :
when I first ping the client from server, then onwards client is able to ping the server,but if client is restarted,its(client) not able to pingthe server.

clients are all assembled ones(non-OEM;PII 32mb SDRAM) and NIC’s are of Intel/d-link Make.
Pls let me know the solution