My MacBook Pro (2006, model A1150) fails to boot beyond the white screen AFTER the screen with the Apple logo and spinner.

I have tried:
Resetting PRAM (doesn't work)
Resetting SMC (how can you tell?)
Apple Hardware Test (says no problems)
Swapping RAM chips with a similar machine (no effect)
Re-installing OS 10.6.3. (Seems to be O.K.)
Booting in "Verbose Mode" (Stops at "Unable to read Block 16 17 18 19" etc)
Booting in "Target mode" (this works!)
Booting in "Safe mode" (this works too!)

What is preventing it from booting, and how can I resolve this matter?

  • Thanks for that. Yes, I did indeed erase the HD before installation.
    – Dave
    Apr 25, 2016 at 18:51

1 Answer 1


When you re-installed the OS, did you erase or repartition the hard drive? The Apple hardware test never found a hardware problem I had with my MacPro so it is not necessarily comprehensive.

The Verbose message sounds like a "can't read the hard drive at block...." message. Which would mean a damaged hard drive.

There appears to be some part of the OS that is stored on the hard drive at a particular place that can't be read at boot time. This part appears to be bypassed in safe mode and target mode.

Good luck!

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