first time linux installation problem

The first time I installed Linux I chose to have Grub, which I understood to be the utility which would allow me to select which operating system to boot, installed on the first partition of the second hard drive, where my Linux install would be. No problems with the install, but when I rebooted the machine I could never get Grub to come up so that I could select which OS to boot. So, I figured I would reinstall Linux but this time move Grub so that it would overwrite the MBR, believing that whoever designed Grub knew enough that if I ran into problems that a solution would be easy enough to find.

However, now when I boot up my machine I am receiving a SMART error on my primary hard drive, telling me that there is imminent hard drive failure and that I should back up my data as soon as possible. Grub would attempt to boot Windows XP but wouldn't get very far before I received errors on rootnoverify and chainloader. I can get into Grub though, working around the SMART error but placing a bootable disk into one of the drives but not selecting to boot from the CD/DVD. That would bring up the Grub boot menu where I could now also select to boot my RedHat Linux. Currently this is the only option that is working for me.