When a section is exported to Excel, by default Interactive Reporting uses the Excel97 format (BIFF8) which supports Unicode (UTF-16LE encoding). In this case no encoding selection is necessary when you export a section to Excel on the Export Section dialog box. (The Encoding drop-down on the dialog box is disabled.)
If you want to continue using the Excel2 format ( BIFF2), you must enable the Excel2 format manually on the General tab of the Program Options dialog box, and select an encoding when you export a section to Excel on the Export Section dialog box.
You set the default Excel format on the General tab of the Program Options dialog box. See Selecting Program Options.