Maybe you can look the internet for hardware compatibily lists, look up if your sata device is supported. I'm guessing it's not and because of that, it can't find any HD to install to. Try to download another live-cd with maybe a newer kernel. I just googled that RHEL5 is using 2.6.22 (someone correct me if I'm wrong).
I7 is rather new I think, so try a distro with a brand new kernel somehing close to 2.6.31 ( I think) Look in http://www.kernel.org
for the latest version.
You could try an Ubuntu live cd maybe 9.10 alpha or beta, just take the latest snapshot. I think Ubuntu is very up to date...
EDIT: in case you're not familiar with linux yet (been there not a long time ago
If you don't really have to use RHEL5 just take a look at http://distrowatch.com/
. There you have an overview of all latest distribution releases. If you click on any distro and scroll down a bit you see what kernel version is used. The beta release of Ubuntu uses 2.6.31 which is the latest stable kernel at this moment. Don't install it immediately and let it boot from the CD then you can check your sound, videocard and see if everything is working properly.
If not you could open a terminal (combination: Alt-F2, then type "gnome-terminal") and type "lspci", this gives you a list of all your hardware available.
If something's not working: copy the output of lspci (in terminal ctrl-shift-c to copy) and paste it here in this thread, someone will be able to help you further!