So you are able to boot into both SuSE and Red Hat, however you cannot login to your Red Hat install... am I understanding this? Or are you having problems with your boot loader? I believe that when you installed Red Hat that it would automatically create a Grub configuration file to accomodate the existing linux install. At least that was an option when I installed RH8 (using the graphical partition software 'Disk Druid'), however I haven't installed it in a while. If you did not specify that you had an existing install of Linux I believe that the Red Hat installation program will automatically install a new copy of Grub on the MBR. So I think that your old Grub files are probably gone now. But that shouldn't matter, because if the installation went well, the RH installer should have created a Grub file which will allow you to boot SuSE or RH. But once again... is that one of your problems? If you can chose to boot into SuSE or RH through Grub, your Grub is functioning properly, the boot loader will not have anything to do with the operation of your Linux installs, or very little. I doubt that a boot loader issue would be the problem with your lack of being able to log in to RH.
Ohh, I just read what you put about using the rescue disk to start Red Hat, so you
are not able to login to RH without a rescue disk eh... Well that probably means that
your Grub configuration is screwed up. To fix that is an interesting bit of knowledge
to obtain, Grub is somewhat complex, but satisfying to learn about.
You should take a look at your grub.conf file which should be located on your boot
partition. (I can't remember for sure, I'm using LILO on this system.) Anyhow I'll bet that when you installed RH it overwrote your MBR (master boot record... where the
boot loader lives) with it's own rendition of what it thought your system looks like.
In the grub configuration file you setup where your boot partitions are and the location of your kernels on the boot partitions. For example you have two kernels
probably that you would like to be able to seperately use, therefore you would tell
GRUB in the configuration file something to this effect...
kernel (hd0,0) ... path to kernel ...
kernel (hd0,3) ... path to kernel ...
where (hd0,0) corresponds to the first partion on the first hard disk, and (hd0,3) corresponds to the 4th partition on the first hard disk (the numbering system begins
at 0, meaning that the first in the series is always # 0)
Anyhousels, the grub config file should display something simular, so that you can boot into 2 seperate distros of Linux.
I really don't believe that you'll have to reinstall everything, I think that it will take
some time and effort to get it working correctly, but that's what Linux is all about.
Check out your grub configuration file and post it, maybe I can read through it and see a solution. As for the password issue, I would do as you said and read through the redhat.com documentation to find a solution. I've never done it before but I don't
think it'll be too difficult.
Excuse the formatting of my reply