Excel 2011 is a Mac version so will not be a .exe file as Macs do not use them.

If I remember aright, the settings are stored in a preferences file but I cannot recall which one at the moment (will have a look later). You might try removing the Free File Opener program if it has an uninstaller, as that should reset the previous preferences. Alternatively you could reinstall Office to reset them, or try the diagnostics (I think those are available in 2011).