You can make Excel always open old spreadsheets in Protected View. Enable or disable Protected View using in-built setting, Group Policy, Registry.

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 ...

That means when you double-click an Excel file on your desktop, a program other than Excel will start and open the document.

Microsoft Excel has an import wizard, but if you structure the text correctly, you can bypass the wizard altogether.