How to administer my sub-networks.

I have 2 sub-network, I want to join in one.
The first one is NT4 clients linked in a Windows 2000 server through a hub, and the second one is a Windows 2000 computer directly linked to the Windows 2000 server (through a netcard).
But i could not “see” the computers of the subnet1, with the one of the subnet2.
How could I manage to access them.