Corrupt HD. Help!

Repair the Hard Drive and Permissions - Yosemite, Mavericks, Mountain Lion or Lion

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. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Repair

When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported then click on the Repair Permissions button. When the process is completed, then quit DU and return to the main menu. Select Restart from the Apple menu.

What happens when you try to repair the disk? Error message? If so what does it say?

Try repairing when booted to recovery mode if not done so already

OS X: About OS X Recovery - Apple Support

Next would be to try reformatting and reinstall the OS

My opinion differs from what lllaass suggests and even from what I used to say.

I say, buy yourself a new drive first, and Install Mac OS X on it, and get your system working again. THEN attack the old drive with the full power of Mac OS X and additional Utilities at your leisure.

Working on saving your drive while working only from Recovery is an exercise in self-abuse. And re-installing onto a drive that may be Bad will torment you.

Start over. Drives are cheap these days.

... and if you do not already have a Backup drive in an external enclosure, get one of those as well. That drive needs to be Big, but need not be very fast -- USB-2 will suffice and that is cheaper. Time Machine is so much better than a complex solution that does not get done often enough because it is too much work.

I disagree. Just because one has a corrupted disk drive directory is hardly reason in itself to spend $60-100 on a new drive plus installing it which can be even more frustrating than repairing yours or even erasing it completely and reinstalling.

Replacing a drive at the first signs of a problem seems an over-reaction.

It is likely not that hard at all to replace your HD. I really can't tell since you did not specify your model MacBook Pro. Find your Mac here and look at the HD replacement video for your model Mac

http://eshop.macsales.com/installvideos/

If you follow the link to OS X Recovery, and links therein, to create and install OS X on another drive (Highly recommended) - you won't be wiping out your system volume. You could if you want. You could reinstall OS X over the old system and leave intack IF and ONLY IF the volume directory and files are good (and that would mean you have a backup, you are using TimeMachine, you bought one or two extra drives: one for backup TimeMachine, one for that clean new install).

OS X: Installing OS X on an external volume - Apple Support

And no matter what, save the OS X Installer, and create your flash installer to boot from and do a clean install or reinstall, so you have a local copy and don't need to download again, or if the version you want is not available.

I recommend Lion Disk Maker X as a place to start and download to create an OS X Installer - sometimes you want to boot from and install onto a new hard drive or erase the entire drive and start fresh - really helpful if the drive has trouble, has Boot Camp, has bad sectors or you replaced with new larger drive or SSD.

How To Make Your Own Bootable OS X Installer flash drive from Ars

http://arstechnica.com/apple/2013/10/how-to-make-your-own-bootable-os-x-10-9-mav ericks-usb-install-drive/

http://liondiskmaker.com/

Nice step by step with photos -

http://osxdaily.com/2014/10/18/clean-install-os-x-yosemite/

A small snippet from the above site:

How to Perform a Fresh Installation of OS X Yosemite on a Mac

1. Back up the Mac with Time Machine or by manually copying your most important data to an external drive – never skip backing up your important data
2. Attach the OS X Yosemite bootable installer drive to the Mac, then reboot as normal

http://osxdaily.com/2014/10/16/make-os-x-yosemite-boot-install-drive/

This allows you to update any version of OS X from Snow Leopard, Lion, Mountain Lion, or Mavericks, directly to OS X Yosemite, with the installer that was just made. You can also perform a clean install (which we separately address in a thorough walkthrough here), or update multiple Macs without having to download it from the App Store again. Be sure to always back up the target Mac before updating OS X, whether to OS X 10.10 or any other version, you can follow detailed instructions on how to prepare a Mac for OS X Yosemite here.

.... ( etc )

4: Perform General System Maintenance

Performing some general system maintenance is always a good idea, so try to make it a habit. We’ve touched on some easy maintenance tips before, and they still apply here. ......

( with cheap disk drive backup storage and built in TimeMachine it should be plug and play to at least have all your files backed up once )

I strongly recommend a 2nd backup clone also, in case of failure, in case you want to boot from #2, or maybe have Mavericks safely bootable and available while you play around with new OS Yosemite. So take a look at cloning - again, easy to use with great interface, and 12+ years of use.

http://www.bombich.com - Carbon Copy Cloner (also on http://www.macupdate.com

It is unwise to repair disks without adequate backups, and lacking that, then I see this kind of scenario:

you need a backup volume

you need a working system

pray that you are not using the drive that needs repairs currently which only makes things worse

The idea of having the system on another drive should be done before there is a disaster or problem.

The fact that Disk Utility cannot says to me, buy a drive, buy two, one for backups using TimeMachine, and one to backup/clone the system or install a fresh system.

In a pinch, you could buy yourself a USB3 drive case, create a partition for your system and create a 2nd partition for backups or to recover files to.

Create a little OS X flash drive installer from the download from AppStore.

http://osxdaily.com/2014/10/18/clean-install-os-x-yosemite/

The forum for MacBook Pro owners is actually here:

MacBook Pro

Upgrading Your MacBook Pro with a Solid State Drive

The answer of Grant Bennet-Alder is correct.