The Windows "Open With" dialog box will help you quickly reassign a default program for your Excel documents.

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 ...

If you cannot open Microsoft Office program files, you can start Word, Excel, PowerPoint, Outlook, Publisher, Viso, etc, in Safe Mode in Windows 11/10.

The Online Tech Tips blog explains how to use a registry hack to add an "Open in New Excel Instance" item to your context menu—which will open your spreadsheet in a separate copy of Excel, so ...