It doesn't sound like the new nic card is bound to tcpip or microsoft client or there is a problem with the new card/drivers.
I assume you are running win95/98.
1. go to Device manager. Under network Adapters you should see the nic card without any yellow exclamation/ red x's. If not then goto network neighborhood. If yes then the nic card is not loaded properly.
2. In network neighborhood you should see the microsoft client, the nic card, the dial in adapter, tcpip for the dial-in adapter, the tcpip for the Nic card, any other protocols or clients. The clients should reflect the Domain/ server they are trying to join. The identification should have a unique computer name and any particular group information.
You said you got the login when dialing. It sounds like you are connecting to the network via the modem and not the Nic card. It has been my expierence that if everything is connected/ configured properly, and I have selected a client as my primary login then when I boot I get prompted for login. If not, If the pc doesn't see the network or is misconfigured it doens't give me a login it goes straight to the desktop.
Good Luck,
Bo