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Prohibitory symbol on Mac startup, although another hard drive partition on the same Macbook works just fine?

The computer: I have a mid 2012 13 inch Macbook Pro with 10 GB RAM and 250 GB space. I have a solid state drive. These specs have not been changed in years. I think my OS is Mountain Lion? Can't remember if I've downloaded Yosemite or not.


The problem: The laptop was working fine until about three or four days ago, when I started experiencing some freezing with that rainbow beach ball for the first time. I also experienced some glitching with windows I had up. Today, my laptop won't reach the Mac log in screen. The start up loading screen with the Apple logo eventually turns into a loading screen with a prohibitory symbol (a circle with a line through it). It never passes this screen.


Relevant observation: I have 50 GB of my computer's hard drive partitioned off with a Windows OS, which I access through holding "option" upon start-up. The Windows partition continues to startup and function normally. So the issue isn't a hard drive problem... [I've had this partition for 3 years. Not a recent thing.]


What I've already tried:

  • Tried to start the computer in Mac "Safe Mode" by holding shift during start up. That didn't work.
  • Ran Apple Diagnostics. The test detected a hardware issue with number: 4MEM/9/40000000: 0x84882f98. Googling this issue suggests I have a Ram problem? I couldn't get a clear answer. Nonetheless, I tried taking out my RAM, putting them back in, trying one and then the other. I even tested a spare piece of RAM I owned. Didn't help anything.
  • Ran the computer in "Verbose Mode" by holding down command and V during startup, but I couldn't really understand the screen so that was a dead end for me.

And I know I'm a sad, silly person, but I do not have the computer backed up. 😟 However, I was able to access some of my more important files on the Mac side through the Windows side to save them on an external harddrive... Anyway, restoring the computer is not an ideal next step.


Please help me. What should I try next? I do not have AppleCare anymore. Thank you so much.

MacBook Pro, Mac OS X (10.7.4), No Mini DisplayPort

Posted on Aug 14, 2015 3:13 PM

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3 replies

Aug 14, 2015 3:17 PM in response to ChasingPaper

Mac OS X- Gray screen or prohibitory sign appears during startup

Reinstalling OS X Without Erasing the Drive


Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears.


Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.


When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the indented Macintosh HD entry from the the left side list. Click on the First Aid tab, then click on the Repair Disk button. If Disk Utility reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit Disk Utility and return to the main menu.


Reinstall OS X: Select Reinstall OS X and click on the Continue button.


Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless and more reliable.


Alternatively, see:


Reinstall OS X Without Erasing the Drive


Choose the version you have installed now:


OS X Yosemite- Reinstall OS X

OS X Mavericks- Reinstall OS X

OS X Mountain Lion- Reinstall OS X

OS X Lion- Reinstall Mac OS X


Note: You will need an active Internet connection. I suggest using Ethernet

if possible because it is three times faster than wireless.

Aug 15, 2015 4:59 PM in response to ChasingPaper

Then either you have no Recovery HD or it's damaged.


Install OS X Using Network Recovery


The following procedure will remove everything from the hard drive.


Boot to the Internet Recovery HD:


Restart the computer and after the chime press and hold down the COMMAND-OPTION- R keys until a globe appears on the screen. Wait patiently - 15-20 minutes - until the Recovery main menu appears.


Partition and Format the hard drive:


  1. Select Disk Utility from the main menu and click on the Continue button.
  2. After DU loads select your newly installed hard drive (this is the out-dented entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.
  3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed. Quit DU and return to the main menu.


Reinstall OS X: Select Reinstall OS X and click on the Install button. Be sure to select the correct drive to use if you have more than one.


Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.


This should restore the version of OS X originally pre-installed on the computer.

Prohibitory symbol on Mac startup, although another hard drive partition on the same Macbook works just fine?

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