Need help.

Install or Reinstall OS X from Scratch

Be sure you have backed up your files because the following procedure will remove everything from the hard 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.

Erase the hard drive:

1. Select Disk Utility from the main menu and click on the Continue button.

2. After DU loads select your startup volume (usually Macintosh HD) from the

left side list. Click on the Erase tab in the DU main window.

3. Set the format type to Mac OS Extended (Journaled.) Optionally, click on

the Security button and set the Zero Data option to one-pass. Click on

the Erase button and wait until the process has completed.

4. Quit DU and return to the main menu.

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

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

because it is three times faster than wireless.

This should install the version of OS X that you had installed.

What version of OS X do you have installed?

Kappy -

daniel.florin said "MacBook Pro, OS X Mountain Lion (10.8.5)".

This is wild a guess, based on the OS he's running and my experience replacing two hard drives: If it's a 2009 or 2010 MacBook Pro 13" the hard drive cable could be failing. This would cause the hard drive to act erratically for both the main and the recovery partitions. When we replaced the hard drives on two 2010 MacBook Pros both ended up with erratic behavior - replacing the hard drive cable on each fixed it.

My other idea is to remove and re-seat the memory modules.

Daniel - Do you have access to another Mac you could use to connect yours to via FireWire? This would allow you to start yours in Target Disk Mode (hold "T" at startup) and run Disk Utility from the other Mac. It might also allow you to back up your drive to an external drive if the drive is failing. (Your computer connected to the other with FireWire, and a USB drive connected to the other for backup. If the other Mac has Thunderbolt you'd need a Thunderbolt to FireWire 800 adapter, plus a F/W 800 cable.) This would not, however, allow you to reinstall the operating system.

You could also remove the drive and install it in an external enclosure to back it up using another Mac.

I recommend Carbon Copy Cloner for the backup, and if you suspect the drive is failing, only back up your user folder(s). You can always reinstall the programs you have, and you'd reinstall the OS on any new drive anyway.

Alternatively, do you have access to anyone who could make you an OS 10.8 installer on a USB stick? This would allow you to start from the USB stick and reinstall the OS, WITHOUT formatting the drive as Kappy suggested, or at least to do a Disk Utility checkup, which might allow you to back up your drive.

Good luck.

- Winston