If you are getting the Data source reference is not valid while trying to create a pivot table in Microsoft Excel, see this post for the fix.

If your Excel files are opening in Notepad on Windows PC, here's how you can reset the settings to make .xls, .xlsx, etc files open in Excel.

Opening XLSM Files in Excel By default, you should be able to open an XLSM file without an issue (as long as you're using Excel 2007 or later), but the macros normally aren't enabled by default.

How to Open Excel 2007 Files As Separate Windows. If you work with multiple Excel files over the course of a workday, and especially if you use a dual-monitor setup, you might wonder how you can ...