Hi JM, As @michoel said, the file format is actually an xml although you set the extension as .xls so when you lunch the file is giving you an alert or an information that your opening an XML file. Microsoft implemented a special handler to view and open those files in corresponding application. This handler looking inside the XML and searches for an XML processing instruction which is named mso-application can specify as progid. In your script equivalent is <?mso-application progid="Excel.Sheet"?>.