Fix for Excel for Mac 2011: “Excel cannot open this file. The file format or file extension is not valid.”

I recently upgraded to Microsoft Office 2011 for Mac. Suddenly I couldn’t open most of my previously-saved files in Excel, and PPT wouldn’t let me save new files. I was receiving errors like this:

Turns out that my hard drive itself had problematic characters in its name; at some point I had inadvertently overridden its descriptive name and replaced it with ‘//’.  Seeing that now, I would have assumed that those characters would be enough to make most any operating system burst into spontaneous dry heaves on the spot. But until the recent MS Office upgrade, both my Mac’s OS (Lion) and MS Office 2008 dealt with the quirky (albeit mistaken) drive name just fine.

Anyway, this is a known bug of MS Office 2011 that presumably will be fixed soon. In the meantime, if you’re receiving this bug, check your folder/directory and core hard drive names to be sure they don’t include any non-standard characters. I renamed my Mac’s hard drive and the issue was immediately resolved.

15 responses to “Fix for Excel for Mac 2011: “Excel cannot open this file. The file format or file extension is not valid.”

  1. Thank you very much. This is really helpful as I wasn’t able to save some of work before I found your fix.

  2. THANK YOU THANKYOU THANKYOU….do you know how long I have been trying to fix this problem…2 years!! So simple!

  3. THANK YOU. Life saver. I owe you.

  4. You are the man!!!!!!!!!! I have been messing around this for weeks and just
    now saw your fix article. In the amount of time it took me to click on the hard drive and name it, is how long it took me to fix it. Thanks again………

  5. THANK YOU. Can’t believe it was this easy to fix. I have been trying to fix this for more than a year

  6. thanks, my daughter loves to mash the keyboard while we are on Skype, almost everything on the desktop has been renamed. and here i was cursing MS again…

  7. This is so common with Microsoft Excel and other office applications… your article is a real lifesaver. I use both Windows and Mac at home and whenever i use an Excel file from Windows on Mac, it cause this issue.

    Thank you so much for the help. really appreciate it.

  8. Hi, I don’t have problem opening the MS files within local drive but the problem is with shared Windows server’s files.
    Error on opening Excel files: file format is not valid.
    Error on opening Powerpoint files: Powerpoint found a problem with content in the file

  9. Thank you! I have been frustrated for months…installing, uninstalling,and found your article! Worked like a charm 🙂

  10. Really thanks man!!! I was using a VM with a windows 7 to open this kind of files…

  11. Excellent, thank you! This has been bugging me for ages and I couldn’t work out why excel didn’t like xlsx files, especially as they sometimes worked. Cheers!

  12. OMG — that’s it. I wasted hours scouring the Internet for a solution to this exact problem, and this was it. Worked like a charm. THANK YOU!!!

  13. I have no problems with my HD my problem is not solved.

  14. Many thanks, fixed my Excel problem!!

  15. Joe Skabeegaboo


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