redhat linux5 lan driver

RedHat 5 was released in 2008, and is based on 2.6 kernel. Network drivers are part of the kernel (more or less). If you are trying this on "modern" hardware, you have little chances of finding drivers for 2.6 kernel (or you have to backport them).

So, the questions you have to answer:
- what kernel version you are using?
- what network adapter you have?