Please ensure the .xls file is not opened in other workbooks, add-ins, or apps. After coming to that conclusion, simply attempt to open the file again in Excel to see if the problem no longer exists.

Excel for Web upgrade Going forward, Microsoft Excel for the Web will now allow users to open and edit large files from SharePoint up to 100MB in size.

If done correctly, Microsoft Excel will open the .csv file, and the results will be the same as with the .txt file process.

Microsoft Word can accommodate a surprising number of file formats, and even take in Excel and PowerPoint data, though it might look funny. Here's how.

Numbers has the ability to open Excel files so you can work on them. You can also export spreadsheets in Numbers so that they are compatible with Excel.