Recovering Bad Hard Disks (CRC on Windows, Error -36 on Mac OSX)

So you’ve been visited by the much dreaded CRC — Cyclical Redundancy Check error, most likely encountered while copying files between hard disks. On Mac OSX, this will usually appear as some cryptic permissions message with an Error -36.

To cut the geek-speak, this simply means that you hard disk may have certain files that may have “bad sectors”, or are corrupted in other words.

Fortunately, this is a common enough problem in our technically advanced world of external storage. I recommend solving this on Windows (I use both XP and OSX Leopard at the time of this writing).

Step 1: CHKDSK

Use what Windows offers you by default. The chkdsk command. Just open an MS-DOS command prompt window and go to the drive you wish to check (I’m hoping you already know your way around a command prompt; if you don’t please consider Step 2 below). With the command prompt showing the drive letter of the disk you wish to check, enter this command:

e:> chkdsk /R

Here, “e:” is my drive to be checked. The “/R” attribute asks the chkdsk command to “recover” whatever bad sectors it finds during its scan. In most cases, and if you’re lucky, this ought to do it.

Step 2: CDCheck (Free)

Only if the problem you were facing still remains after you have run the chkdsk command, should you consider doing this. This is a freeware program that makes it super-easy to check/recover your disk. It can be any disk–your current hard disk, a CD or a DVD, or even an external hard disk. The interface is pretty simple as you can see in the screenshots here.

Step 3: SpinRite (US$ 90)

If all else has failed, just save yourself some heartburn and go straight to SpinRite. This is hands-down the best software for this purpose, as anyone in a dire need of data recovery will confirm. I would trust any piece of software from GRC. Only catch: it’s not free, but when you use it you know why it’s worth every last cent. It gives you a simple option to save an ISO file, which you can then easily burn on to a CD using any CD writer tool (including Windows’ own right-click). Then reboot your machine so it starts from the CD. SpinRite will automatically report and recover whatever is recoverable.

Next Steps

Basically, a CRC error is the beginning of the end. If this is on an external hard disk, I highly recommend that you consider backing up the data immediately.