Hi everyone,
I’m new to the forum and I’m facing a serious issue with one of my backup files. I’m using FBackup version 9.9 and trying to access a ZIP file located on my external drive: E:\dailydata critical\1_d.zip
When I try to open it, Windows shows the following error: “Windows cannot open the folder. The compressed (zipped) folder is invalid.”
I read that ZIP files over 4GB might use ZIP64 format, so I reduced the data size to 2.474 GB, but I still get the same error.
What’s strange is that other backups with the same naming format (like x_d.zip) open just fine—even one that’s over 6 GB works without issues.
I don’t have any scheduled tasks on this computer, and this file contains critical data I must be able to restore if needed. I’ve tried everything I can think of, but no luck.
Has anyone experienced this or found a solution? Thanks in advance for your help!
Cannot open critical backup ZIP file
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definitiontwo
- Posts: 1
- Joined: Wed Oct 15, 2025 8:00 am
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Adrian (Softland)
- Posts: 2061
- Joined: Thu May 23, 2013 7:57 am
Re: Cannot open critical backup ZIP file
Hi,
If Windows cannot handle that file, please use WinZip, WinRar or 7zip to open it.
If Windows cannot handle that file, please use WinZip, WinRar or 7zip to open it.
Do you know you can monitor your backups remotely with Backup4all Monitor? You can read more here: https://www.backup4all.com/backup4all-monitor.html
Re: Cannot open critical backup ZIP file
Hello 
This sounds like a corrupted ZIP file rather than a size issue. The fact that other larger backups work fine confirms it's not about ZIP64 format.
Try opening the file with 7-Zip instead of Windows' built-in extractor. Download it (it's free) and right-click on your 1_d.zip > 7-Zip > Extract here. 7-Zip is much better at handling corrupted or partial ZIP files and might be able to recover at least some of your data.
If 7-Zip also fails, try the "Test archive" option in 7-Zip to see exactly what's wrong with the file. It'll tell you if the file is partially recoverable or completely corrupted.
Another option is using a ZIP repair tool like DiskInternals ZIP Repair or similar software. They can sometimes reconstruct damaged archives.
For the future, consider enabling backup verification in FBackup settings to catch corruption early. Also, keep multiple backup versions instead of relying on a single file for critical data.
Hope you can recover your files!!!
This sounds like a corrupted ZIP file rather than a size issue. The fact that other larger backups work fine confirms it's not about ZIP64 format.
Try opening the file with 7-Zip instead of Windows' built-in extractor. Download it (it's free) and right-click on your 1_d.zip > 7-Zip > Extract here. 7-Zip is much better at handling corrupted or partial ZIP files and might be able to recover at least some of your data.
If 7-Zip also fails, try the "Test archive" option in 7-Zip to see exactly what's wrong with the file. It'll tell you if the file is partially recoverable or completely corrupted.
Another option is using a ZIP repair tool like DiskInternals ZIP Repair or similar software. They can sometimes reconstruct damaged archives.
For the future, consider enabling backup verification in FBackup settings to catch corruption early. Also, keep multiple backup versions instead of relying on a single file for critical data.
Hope you can recover your files!!!
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Adrian (Softland)
- Posts: 2061
- Joined: Thu May 23, 2013 7:57 am
Re: Cannot open critical backup ZIP file
Hi,
If the zip file is corrupt, please scan the C: drive for errors as it's used as temp folder.
Also consider testing the RAM memory by creating a zip file larger than the size of your RAM, using WinZip or 7zip.
If the zip file is corrupt, please scan the C: drive for errors as it's used as temp folder.
Also consider testing the RAM memory by creating a zip file larger than the size of your RAM, using WinZip or 7zip.
Do you know you can monitor your backups remotely with Backup4all Monitor? You can read more here: https://www.backup4all.com/backup4all-monitor.html