It is an executable file, it can be run, double click on it and it should install Avast.
Why is it that you are trying to open it ?
OK I see the Windows interface will show Open (presumably you right clicked this), see attached image, click to expand,
I can only assume you are trying to install avast ?
If so double click it or right click it should have an option to Run as Administrator. I have never needed to do this, I would just double click on the file.
When you are trying to do this is it on a User with Administrator privileges ?
