A cyclic redundancy check, or “CRC” error, indicates a bad spot on your hard drive. The fact that you see it when trying to copy a file indicates the bad spot may be within the file itself.
We need to verify that, try to recover your file, and repair your hard drive.
Then we need to learn from this.
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In the file or not?
We’ll start by making sure the problem is actually with the file being copied, since it’s also possible the problem is with the hard disk location being copied to.
It’s a two-step process using Command Prompt.
- “CD” to the folder in which the file resides.
- Copy the file to NUL.
NUL is a special device file name that means “nothing”, so this operation copies the file to “nothing”. This is helpful because we know the only disk access that will happen is to read the file; there’s no attempt to write to the disk.
First, locate the file. If you’re not sure where a PST file is, Where is my Outlook “PST” file located? has instructions to find it. As an example, my file is at “C:\Users\lnote\Documents\Outlook Files\Outlook.pst”.
Run Command Prompt, and enter the two commands corresponding to the two steps we listed above:
CD “C:\Users\lnote\Documents\Outlook Files\”
copy Outlook.pst NUL
(Replace my example location or file with yours, of course.)
If a copy to NUL works without reporting an error, the problem is likely not with the file itself, but with the location you were trying to copy it to. My recommendation would be to copy it to a different disk entirely — perhaps a USB stick, external drive, or something else.
If the copy to NUL fails with a CRC error, then we’ve confirmed the bad sector on your hard disk is actually being used by some portion of the file.
Try to fix the file
If the problem is in the file itself, we start by making as best a copy of it as we can. This preserves a copy in a state where “it can’t get any worse than this”. Some data within the file may be lost, but you’ll have copied as much as possible before taking any additional recovery steps.
Once again, we want to copy the file to a different disk, and once again, this is best done within Command Prompt.
CD “C:\Users\lnote\Documents\Outlook Files\”
xcopy /c Outlook.pst D:
(Replace my example location with yours, and the “D:” drive with the drive letter assigned to the other drive to which you’re copying the file.)
Two important things to note: we’ve used the xcopy (for eXtended copy) command, and we’ve added the “/c” switch, which keeps copying even if errors are encountered. As you’ve already experienced, the default behavior of both COPY and XCOPY, as well as copying a file using Windows File Explorer, is to stop if an error occurs.
Now that we’ve got a “no worse than” backup copy, we can attempt to repair the disk.
Try to fix the disk: disk surface recovery tools
If you’re willing to spend money, there’s a possibility we can repair the hard drive.
Tools like SpinRite analyze your hard disk and repair sectors without modifying its contents. If SpinRite runs on your machine (sadly, it may not on more and more machines, as it’s not been updated in some time1) and a bad sector can be recovered, it’s very possible that SpinRite, or other tools like it, will recover it.
Running tools like this is not without risk. If your disk is on the verge of failure, the heavy use in analyzing and recovering the data could push it over the edge into a more catastrophic failure.
Try to fix the disk: CHKDSK
If surface analysis and repair tools don’t do it, then Window’s own CHKDSK utility is the next thing to try. It’s not as thorough, and it doesn’t perform the same deep analysis and recovery, but it can recover from some types of failures.
Once again, in the Command Prompt:
The “/R” parameter — for “Repair” — directs CHKDSK to check for disk physical and surface errors and repair them as best it can.
If this is your system drive (most often C:), the command will not run immediately, but will be scheduled for the next reboot. You’ll need to reboot to make it happen.
After CHKDSK is done, try making another copy of the file. If it works, save that as a possibly fixed copy of your file.
Even if CHKDSK does repair the problem, I’m torn on how much you can trust the hard disk. You could still experience future failures. Given that disks are relatively inexpensive in comparison to data loss, I’d be tempted to replace the drive, especially if this is not the first instance of an error.
When all else fails
If none of the steps above repair the bad sector or otherwise recover your file, you’re a little bit screwed.
It’s now time to work with the best-effort file you saved earlier and, depending on what kind of file it is, try to recover the contents. In your example, an Outlook PST file, that means running scanpst on it, which will scan the contents of the file and attempt to recover what it can. There will most likely be data loss — sometimes a lot of data loss.
That’s why I encourage you to never run utilities like scanpst on your only copy of the file. You always want the original to go back to in case there’s something else in it you can recover manually.
For other types of files and applications, it’ll depend entirely on the specifics of that application as to how it deals with a partially corrupt file and whether it can be repaired.
The lesson to learn
Which brings me to my last point.
If this is the only copy of the file — if you will suffer significant data loss if this file has been damaged — then apparently you haven’t been backing up.
Start. Backing. Up. Now.
This was a wake-up call. Even if you successfully recover your file, you should be scared.
Start backing up your important data. Now. In fact, start backing up everything, whether you think it’s important or not.
The next time there’s a problem, you may not be as lucky.
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