Solved Can't Open xlsx file - file format or file ext not valid

April 25, 2013 at 20:17:46
Specs: Windows Vista
A friend created an Excel spreadsheet at work and when trying to open it at home it wouldn't open. Comes up with "file format or filoe extension not valid. Verify that the file has not been corrupted..". Using Office Home & Student 2010 on two different computers with different OS's (XP, & Vista 64bit) with the same result. Xlsx files created at home and taken to work can be read on the same USB stick, but anything created at work comes up with the same error. Any ideas?

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April 26, 2013 at 05:21:48

Change the file extension manually from .xlsx to .xls and try again to check the issue.

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April 26, 2013 at 12:44:54
Thanks for the quick reply. I changed the file extension to .xls and a slightly different error came back...."File is in different format than specified by the file extension." So it seems that the file extension is correct at xlsx. I changed it back to .xlsx and it came back with the same error.

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April 26, 2013 at 14:20:19
✔ Best Answer
IF the files were created at work and can be read only at work there may be a digital certificate that the good people in IT installed on your work machines so that with out the digital certificate the files cannot be accessed.

See here for more info:


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April 26, 2013 at 14:54:51
Yep, I'll bet that's it. I'll have her check with her IT person at work to verify that, but I feel confident that is the problem. Thanks for your help.


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April 29, 2013 at 13:10:03
Re #1.

An xlsx file is compressed. It will therefore not work if changed to xls as that is NOT a compressed file.

Always pop back and let us know the outcome - thanks

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