Install grub on the MBR of the hard drive - grub calls it (hd0) ... you should be able to do that from the installation disk without having to reinstall RHEL
The only time you need to install grub onto a partition (such as /dev/sda8) is when you have a bootloader installed onto the MBR which will chainload to the bootloader on the partition.
EDIT:
start the computer with the installation disk and select rescue mode. From the command line type:
Code:
grub
root (hd0,7)
setup (hd0)