Close all other open programs Give the workbook a different name Disable Excel add-ins Use the Share feature in Excel Update Office Repair Office. 1] Close all other open programs The first thing ...

If you cannot open an Excel file and see Excel cannot open the file because the file format or extension is not valid error, see this post.

How to Open an XLS File in Excel. XLS files are Excel workbook files created in Excel 97 or Excel 2003. The 2007, 2010 and 2013 versions of the program use the XLSX format by default to save ...

Also, if you're using multiple versions of Excel on the same computer, the default program for opening your files may be a different version of Excel than you'd prefer to use.