Is my Hard Drive Dying?

Hi, I cannot boot from my hard drive when it is connected internally in my 13" Macbook Pro (2009). Also, when running disk utility off the install DVD it does not detect the hard drive. However, when booting via USB to an external HD enclosure, it works fine. Also, I have taken the hard drive that used to be in the external enclosure (I use it for Time Machine Backups), and have connected it internally and it is detected by the computer after booting. Also, I repaired permissions when I got it to boot up when connected externally and that seemed to have no effect.

Is my hard drive beginning to die? I have been using it for just over a year and it has performed flawlessly. The only thing I can think of is that maybe the hard drive is beginning to go and if it is receiving more voltage when connected via USB that is what is allowing it to still work.

Cliff Notes:
-Cannot boot when hard drive is connected internally, and disk utility does not see hard drive. (2009 13" MBP)
-Hard drive will boot fine in external enclosure
-Time Machine hard drive that used to be in external enclosure is detected fine when connected internally.

It does sound like it may be starting to go. Did you try booting from it internally again after testing it in the external enclosure just to see if it was a loose connection?

Stretch said:

It does sound like it may be starting to go. Did you try booting from it internally again after testing it in the external enclosure just to see if it was a loose connection?

Click to expand...

Yes, and it still gives the same results. I also tried putting it into into a PC laptop, and while it obviously wouldn't boot, the HD is recognized in the bios. So now I am very confused.