Old 2xPII Servers - slow network speed

Hello all,

I have 2 dual core pentium 2 old servers. On this 2 servers is installed Windows NT 4.0 Server (Primary Domain Controler and the second is Backup Domain Controler).

The problem is that in this moment the transfer of files in the LAN is not bigger that 3-4 Mbytes/s.

I mention that 30 workstations are connected to this 2 server and the working in the LAN is becoming very difficult when all the workstations are connected to the servers.
I bought a switch Allied Telesyn AT-FS750/24 (10/100TX x 24 ports WebSmart switch with 1000T/SFP x 2 combo ports) but the speed was increased insignificant.
I bought 2 TP-Link TG-3269 (10/100/1000M PCI Adapter) thinking that if I connect them to the 1Gb ports at the switch the speed will be increased - no success even worts.
When I tried to copy a bigger file from the server I realized that the processor on the server is 90-100% loaded.

How can I improve the speed transfer in the LAN? What network cards should I buy for the servers?
Do you have any other solutions other that buy 2 new servers?

Thank you in advance.

with regards,
Dragos

Thank you for reply.

Yes, you are right. Sorry. It is a dual processor Pentium 2 with dual processor motherboard and not a dual core processor.

Since the processor is loaded 70-100% in transfers, I am sure it is a good transfer speed for the actual situation.
I am still wondering if I can find a network card that use less from the CPU.

with regards,
Dragos