Windows doesn’t have a built-in way to change icons for exe files. It isn't as straight-forward as changing the icon of the shortcut unfortunately. You need to use a third-party application called ''Resource Hacker'' to access and modify the exe properties because the icon is embedded in its resource table. Take caution as doing this invalidates the exe's digital signatures and may cause it to brick. If you still want to proceed: 1) Create a backup copy of firefox.exe 2) Install Resource Hacker utility 3) Open the exe in Resource Hacker 4) Find the Icon folder, then replace with an icon of your choice