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.

When you see the Photos can’t open this file because the format is unsupported or the file is corrupted, you can fix it in the following ways. Make sure the file format is supported Check if the ...

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 ...