How do I fix a cyclic redundancy check error when I try to copy a file?

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Summary: CRC errors happen when there's a bad spot on the media of your hard disk. Data recovery and disk repair are often possible with the right tools.

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The cyclic redundancy check, or "CRC" error, indicates a bad spot on your hard drive. The fact that you're seeing it when you try to copy a file indicates that the bad spot may be within the file itself.

We need to verify that and then we need to try to recovery your file and repair your hard drive.

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First, let's make sure that the problem is actually with the file you're copying since it's equally likely that the problem is with the location you're copying too. This is easy. Fire up a Command Prompt window, and then copy the file to NUL:

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\>CD (to wherever the file is located)

C:\wherever>copy Outlook.pst NUL
1 file(s) copied.

This reads the entire file by copying it "nowhere". If this succeeds, the problem is not actually with the file itself, but the location you were trying to copy it to. My recommendation would be to copy it to a different disk entirely, or a different machine on your local network.

If this copy fails, then we've confirmed that the bad sector on your hard disk is actually being used by some portion of your file.

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Now that we've confirmed that the problem is in fact in the file itself, we need to make as best a copy of it as we can, somewhere else. This sets a position of "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 the recovery efforts.

Once again, we want to copy the file to some different hard disk, or some other machine on your local network. And once again we need to do this within the command prompt:

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\>CD (to wherever the file is located)

C:\wherever>xcopy /c Outlook.pst D:
1 file(s) copied.

Two important things to note here: 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 is to stop if an error occurs.

Now that we've got a "no worse than" backup copy, we can start attempting to repair the disk.

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If you're willing to spend $89 (as I write this) then there's a very good chance we can simply repair the hard drive.

I'm a huge fan of SpinRite.

SpinRite is a hard drive recovery and maintenance program. When you run it, it will perform a lengthy and exhaustive analysis of your hard disk without modifying its contents. Exactly how it does what it does is probably too technical and lengthy for this space, but one of the most important things that it does is simply this:

If a bad sector can be recovered, SpinRite will recover it.

And many, though of course not all, bad sectors can be recovered using SpinRite.

The net result is that after running SpinRite on the drive, it will either recover the sectors and you'll have a good, working hard disk once again, or it won't - and you'll know with some confidence that the disk cannot be recovered.

In the first case, if SpinRite is actually able to recover the sector for you, then unless SpinRite tells you otherwise, I'd then happily reboot and continue using the hard drive.

If SpinRite is unable to recover some data on your hard drive, I would first reboot into Windows and, as we did above, make another copy of the file. While SpinRite may not have recovered all the bad sectors on your hard drive, it could have repaired some, and those might have been the ones causing the problem with the file you're trying to access. I would not overwrite our first "no worse than" copy, but I would save this new file, as a kind of "possibly better" copy. And then I'd plan on replacing the drive.

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If you're not up for spending the money for SpinRite, then Window's own CHKDSK utility is the next best thing. It's not as thorough, and it doesn't perform the same deep analysis and recovery as SpinRite, but it can, in fact, recover from some types of hard disk failures.

Once again, in the Command Prompt:

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\>CHKDSK /R

The "/R" parameter indicates that CHKDSK should check for errors and repair them as best it can.

Important: if this is your system drive (most often C:), this command will not actually run the operation immediately, but will schedule it for the next reboot. You'll need to reboot to actually make it happen.

After it's done, try making another copy of the file. If it doesn't work, then obviously CHKDSK wasn't able to repair the error you're experiencing. If it does, however, save that copy as a possibly fixed copy of your file.

Even if CHKDSK does repair the problem, I'm actually torn on how much to continue to trust the hard disk. You could still experience future failures.

Though I suppose that's true for any hard disk, after any utility is used. Or not.

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At this point, if none of the steps above have repaired the bad sector or otherwise recovered your file, you're just a little bit screwed.

It's now time to work with the best-effort file that 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 most likely will 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 that 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 will deal with a partially corrupt file, and whether or not it can be repaired.

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And that brings me to my last point.

If this was your only copy of the file - if you would have suffered significant data loss had this file become corrupt - you haven't been backing up.

Start.

This was a wake-up call. Even if we successfully recovered your file, you should be very scared.

Start backing up your important data. Now.

The next time there's a problem, you may not be as lucky.

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• Cyclic Redundancy Check: what is it, and how do I get rid of it on my newly burnt CDs and DVDs?< Cyclic Redundancy Check is an error detection mechanism to make sure that your data has been read properly. If a Cyclic Redundancy Check fails, it could mean several things. /p>

• How do I fix a bad sector on my hard drive? You should try to fix bad sectors on your hard drive before trashing it. Starting with "chkdsk" may help.

Article C2935 - February 15, 2007