Help w HD issue. The volume Macintosh HD could not be repaired

Did you reset the PRAM? Start with that if you have not. Press: +Option + P + R while the system is booting up, before the Apple logo. Keep holding until the start up chime rings twice.

If you already did that then start the machine in Target Disk mode and try and repair the volume from another Mac....

Those are where I would start.

Also, what Mac do you have, and what OS is it running?

 

It should be labeled Command/CMD//or have a weird little gear kind of icon and should be the first key to the left of the space bar.

You can also try to reset the SMC if the PRAM/NVRAM reset does not work:

1. Shut down the computer if not already off.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.

 

Don't worry about resetting PRAM. It has absolutely nothing to do with your problem. Neither does restting the PMU/SMC.

Here is what I would try. First, boot up in Single User Mode and run fsck.

1. Power on Mac while holding Command + S
2. When the prompt comes up, type in /sbin/fsck -fy and hit Return
3. After it is done, then you can hit return to finish booting. Basically this is running a Disk Utility style repair on the drive before booting the Finder.

You can do this if you can't use the recovery partition for Disk Utility (10.7 and later which you should be running on a 2012) or you cannot boot the Mac off your install CD and run it from there. You can boot to the recovery partition by holding down Command + R when you power it on.

If that doesn't work you may need to try some 3rd party program to fix the drive.

 

They may or may not help at all in the end, but they are so easy to do compared to any other troubleshooting they are always a first step.

All this said, running the repair you mention is clearly valid and would be the next step if I were doing it too.