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

If you see The file couldn't open in protected view error while opening Microsoft Excel, the fixes listed in this post will help you.

How to Tell If a Worksheet Is Protected in Microsoft Excel 2003. Protecting a worksheet in Excel 2003 prevents others users from editing it. For example, if you have tracked and charted your ...

Microsoft Excel normally does not let users change the values of protected cells. To edit a protected cell, you must first remove its protected status.

How to enable Protected View in Excel 365 First, launch Microsoft Excel 365 and then select the Options button from the Home screen.