Can Windows NTServer 4.0 be used as a ga

We are using Server 4.0 on a local network. Three machines access this as a file server. The machine has 2 NIC cards one is a thin net (BNC) the other is a RJ45 NIC that is used for internet access. From the server I can see the whole network (including the local network) but from the three machines on the local network I can only see them and the server. They will not see the whole network. I know that installing a mini hub would take care of it but they want access now. (no money until the 1st of theyear) Can anyone help.

Thanks
Will