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.

When launching Excel via Task Scheduler, specify EXCEL.EXE as the main program, and the path to the file that you’d like to open as the ‘argument’.

Resetting the Registered File Types for Excel. When you first installed Microsoft Excel, it should have registered itself as the default program for opening compatible file types, such as .xlsx or ...