seeing as RHEL5 is not free and you MUST buy a license and support contract
Have you asked red hat about your network card ?
normally there is NO NEED to build a "driver"
also for a "driver" you will need to do more than just
./configure && make
you will need a bunch of code to built that
most should be installed from
yum groupinstall "Development Tools" "Development Libraries"
yum install kernel-devel