Ditto on that. Recently had to setup Scientific Linux 5.2 (RHEL5.2 clone) on a 780a motherboard, and this option was required for the installer to see the hard drives at all.
I haven’t setup RAID with RHEL5, so I can’t help you there. I just had one disk and did the default format. The hard drive controller on 780a motherboards does not work with the driver in RHEL5 unless you use the pci=nomsi kernel option.
Right as you boot off the CD, it will say “type linux to install, or type linux text to install in text mode” or something like that. type linux text pci=nomsi and you should be in business.
Don’t know about a CD, probably? I think I’ve done it off of a USB stick before, but now I’m not sure if that was actually on that motherboard or another one…