Results 1 to 7 of 7
  1. #1
    Bronze Lounger
    Join Date
    Jun 2001
    Location
    New York, New York, Lebanon
    Posts
    1,449
    Thanks
    1
    Thanked 1 Time in 1 Post

    Repairing a Zipped Archive

    <img src=/S/hello.gif border=0 alt=hello width=25 height=29> Loungers

    I am looking for a utility that can repair WinZip Zipped Archives.

    I have such an archive that can be unzipped, but when it comes to a MS-Word document, it tells me that it could not continue. Something about a checksum being invalid.

    I tried opening the document from within the archive, and it failed as well.

    Any suggestions?

    Wassim
    <img src=/S/compute.gif border=0 alt=compute width=40 height=20> in the <img src=/S/bagged.gif border=0 alt=bagged width=22 height=22>

  2. #2
    Plutonium Lounger
    Join Date
    Mar 2002
    Posts
    84,353
    Thanks
    0
    Thanked 29 Times in 29 Posts

    Re: Repairing a Zipped Archive

    If you do a Google search for 'PKZIP DOS Download' (without the quotes), you'll find many sites where you can still download PKZIP for DOS, for example http://www.frostburg.edu/admin/acacom/shar...3.x/pkz204g.htm. This comes with a utility PKZIPFIX that can repair .zip archives. You'll have to use the Command Prompt, PKZIPFIX is not a Windows program.

    If you would prefer something for WIndows, do a Google for 'zip repair utility' (without the quotes), or something like that.

  3. #3
    Uranium Lounger
    Join Date
    Dec 2000
    Location
    Salt Lake City, Utah, USA
    Posts
    9,508
    Thanks
    0
    Thanked 6 Times in 6 Posts

    Re: Repairing a Zipped Archive

    Wassim, if a ZIP file is seriously munged, the contents are almost always unrecoverable. I don't know if the evaluation versions of PKZip come with recovery capability, go ahead and look. If you wish, PM me and we can arrange that you e-mail it to me and I'll have a shot at recovery with registered PKZip 5.5.
    -John ... I float in liquid gardens
    UTC -7ąDS

  4. #4
    Gold Lounger
    Join Date
    Dec 2000
    Location
    New Hampshire, USA
    Posts
    3,386
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Repairing a Zipped Archive

    I just performed the following experiment:

    1. I made a copy of a .zip filem let's call the copy Bad.zip.
    2. I used a hex editor to change an arbitrary bye in the file.
    3. I tried exploding the Bad.Zip with Stuffit Expander 6. I got a nasty mesage stating that the file had a CRC error.
    4. I then tried expanding with ZIPCentral. ZipCentral also reported a CRC error.
    5. I then tried the Repair in ZIPCentral, it did Repair, but the file was corrupt and Excel could not open the workbook that had been zipped.

    However, ZIPCentral has been able to repair other files.

  5. #5
    Gold Lounger
    Join Date
    Dec 2000
    Location
    New Hampshire, USA
    Posts
    3,386
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Repairing a Zipped Archive

    I Just tried PKZIPFIX on the file I referenced in the other posting.


    No luck.

  6. #6
    Platinum Lounger
    Join Date
    Nov 2001
    Location
    Melbourne, Victoria, Australia
    Posts
    5,016
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Repairing a Zipped Archive

    Hi Howard

    It has always been my understanding that zip archives can only be repaired if the damage is in the index/ headers of the archive itself, not in the files contained therein. For instance, if the headers incorrectly report information about the size of one of the files, this can be corrected, thus allowing the archiver to extract files correctly etc... I'm not sure of all the details, but here are some typical messages from PKUnzip, indicating damage - some repairable, other not:

    PKUNZIP: (W[01,02]) Warning! File has bad table

    The Imploded file being tested or extracted has an error in its encoding.
    The file is probably corrupt or not a .ZIP file. Files that have been
    damaged in this way cannot be recovered.

    PKUNZIP: (W03) Warning! File has bad table

    The Reduced file being tested or extracted has an error in its encoding.
    The file is probably corrupt or not a .ZIP file. Files that have been
    damaged in this way cannot be recovered.

    PKUNZIP: (W04) Warning! XXXXX.ZIP - error in ZIP, use PKZIPFIX.

    The named .ZIP file has a corrupted file index. Use PKZIPFIX to
    reconstruct the .ZIP file. You may also receive this message if you
    attempt to extract a file which is not a .ZIP file.

    If the file is less than 22 bytes in length it cannot be a .ZIP file and
    the "use PKZIPFIX" message will not be shown.

    But I'm not surprised that the repair utilities were unable to rectify the "damage" you did altering a random byte value. I can't see any way of them knowing what to change back to what to make a CRC checksum correct again! <img src=/S/grin.gif border=0 alt=grin width=15 height=15> My guess is that the byte you selected to change was part of the XLS and changing it corrupted the workbook, in the same way it would had you altered the actual XLS in this manner.

    Alan

  7. #7
    Gold Lounger
    Join Date
    Dec 2000
    Location
    New Hampshire, USA
    Posts
    3,386
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Repairing a Zipped Archive

    I agree, that's why I "randomly" chose to change a bit that appeared to be part of the file, not in headers, etc.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •