2] Use the Open With option. Another attempt you can make to open the file in Excel when Notepad is trying to read it is to use the Open With option.

Open Excel files in separate windows with the Office Tab; 1] Open Excel files in separate windows using the Shift key and the Taskbar. Have your first Excel workbook already open on your computer; ...

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 workbooks, but can also use the XLS format.