Hard-drive not recognised. Drive and cable good. Logic board failure?
I recently got the flashing on-screen grey question mark problem with my device failing to boot up. I booted up from the Snow Leopard DVD and found that my hard-drive was not appearing in Disk Utility. I transferred the hard-drive to my wife's 2012 MacBook Pro, which could read the drive without any problem, but my 2009 MacBook Pro could not read hers. I also tried switching the hard-drive cables between the Macs and found that the 2012 MacBook Pro could read the the hard-drives using the cable from my 2009 MacBook Pro. (I would have checked the 2012 cable on my 2009 MacBook Pro too, but the cable's too short.)
It seems to me that my hard-drive and the hard-drive cable are both fine. Does this mean that the logic board is wrecked, or is there something else I should check?