ico must have more than one png inside for it to be classified as an icon according to a function I use. Just make sure your icon comes with a range of sizes embedded in one. (Hint: when you open your icon using windows photo viewer, there must be left right arrows to show all png files the icon has). sizes must be a multiple of 16, can be 16x16, 32x32, 48x48, 64x64, 128x128, 256x256, you can just use 1 png but make sure it is resized into many sizes and put together to make it an ico. Why is it that when you use reshacker, when you check rt_icons, you find many icons but when you check rt_icon_group you find a set of icons in one.
https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx