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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
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! 
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
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