i386 most certainly is the wrong architecture for your hardware as it only supports Intel 80386 compatible CPUs. Look for the i686 kernel-smp package, which supports multiple CPUs.
Also install all errata packages for Red Hat Linux 7.3, which has reached end-of-life long ago, and take a look at
http://fedoralegacy.org where they provide additional security updates for Red Hat Linux 7.3, including bug-fixed kernel packages.