For me the only reason you'd use and infererior RedHat-based distros is if you had commercial products that required RHEL. Well now im in that situation, so CentOS 4.6 it is, and its not as hard as I thought.
- Find the boot.iso on one of the mirrors (it should be located in centos/4/os/i386/images/) I used http://isoredirect.centos.org/centos/4/os/i386/images/boot.iso
- Choose text linux at the boot loader
- Select HTTP install
- For the IP address enter the name of your mirror (I used isoredirect.centos.org) and the path (/centos/4/os/i386/) and it should find everything you need