Hi, redhat is great, but I would suggest you try a live CD, like knoppix, mandriva2008 and many more. You do not have to install them, just boot it once it runs you can be able to mount / open your hard drive; you can also resize it to create space for your new linux box.
I had an HP Machine that would not boot any linux distribution until I got Mandriva 2008, my conclusion was "The hardware in use on this particular machine was not yet supported" and looking at the version of redhat you tried to install I suspect the same problem I had. So download the latest distro and sit back and see magic.
