Add lineslike the following to the bottom of grub.conf
title RHEL4 (2.6.9-5.EL)
kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/ rhgb quiet
You may need to change the initrd name in the last line (because I'm guessing), and the root= could be better as root=/dev/hda5 ...
Of course, why you would want
to pay for the enterprise version as well as install fedora is beyond me... and your business entirely.