Well, yes and no. By default, Windows displays icons for file types based on their extension. Some file types such as .exe, .ico or .cur can have different icons, which are based on the internal contents of a file.
Icon customizing applications can override the default behavior and can enable different icons for individual files. (RW Icon Editor is an icon creation tool, not a Windows customization tool). If you are running such a customization tool, you'll have to look at its documentation.
If you are not using any icon changers and still want to have custom icons for .exe files, you can use these methods:
1) Create a shortcut and customize its icon from its properties dialog.
2) Replace an icon in an executable file from RW Icon Editor. Before you attempt this method, backup the .exe file in question. There is no undo!