ASRock boot problems

One of my hard disks started to report IO errors.  Since I manually mirror files onto different disks, I know I wouldn't lose any data.  I started the process of adding a 3rd mirror for all the files on that disk, so that when it dies, I will still have two mirrors of all the files.  About two weeks later, I come home and the computer is unresponsive.  I try rebooting it, and the ASRock boot screen comes up, but it doesn't move on from there.  I tried powering it off for a few minutes, just in case it overheated.  It still didn't work.  Then I remembered the time I left a Wii disk in the dvd drive.  The bad hard disk must be preventing the computer from coming up.  I opened the case up.  I have 7 hard disks in this computer, so there was no way of determining which disk was the bad one just by looking at it.  I unplugged all the SATA cables and turned the computer on.  It beeped and the GRUB boot screen came up.  I turned the computer off, plugged in a single SATA cable and turned the computer back up.  I kept doing this until the GRUB screen no longer came up.  I took that disk out and it was the right one.  I guess ASRock motherboards are very sensitive to bad boot devices.