How to know whether the network driver alredy installed in my system

Linux and Unix-Like Red Hat
1

I am using NVIDIA nforce: Networking controllers

And Redhat enterprice linux ws version 4 32 bit: OS

I want to connect my system to Broadband internet using linux.

From where can I download the driver for nertwork.

How to know whether the network driver alredy installed in my system.

Thanks
Rijas PA