I dont remember If I downloaded the Standalone Executable or the Windows Installer when I installed the 3.3.6 version. Does it matter and can I download either one to perform the update?
The difference between these two is that the standalone excecutable does not create any files inside Program Files, but it loads and saves wallet data to Electrum folder located in %appdata% just like the installed version. Take a closer look at the Electrum icon. Is it a shortcut to Electrum folder in Program Files? If so, download the installer.