I am guessing the anaconda installer from Fedora to RHEL differs a bit and may not include more modules. Also RHEL3 is closer to Fedora 1 using 2.4 kernel and RHEL4 is closer to Fedora 3.
Now I would think RHEL4 supports sata but the installer lacks the modules to load it. Here is a post that mentions the bios change and another way I did an install a while back. I had to install to an IDE drive. Copy partitions to sata and install grub on the sata. http://www.linuxquestions.org/questi...75#post2077075