You are using the wrong kernel rpm. Don't use the highmem rpm since that one isn't meant for your rh 7.3 distro. It is meant for a special rh 7.3 distro with support for gigabytes of memory. (likely > 4 GB)
Just use: NVIDIA_kernel-1.0-2960.rh73up.i386.rpm
It doesn't really matter which one you use.