"Big Al" wrote

| Windows uses ICO files and an ico can contain many different sizes,
resolutions, or images in that one file. If you had an icon editor like
| Greenfish Icon Editor Pro,(free), you could make your own, and it would
show that you can make 32bit color, 8bit color etc. and sizes 8x8 up
| to 256x256. Most icons come in several sizes so toolbars can use the
small, the desktop can use various sizes as well as explorer using
| several sizes.
|
I think that it can also be a PNG in newer Windows versions,
but I don't know the details of how that works.

| To Arlen, I have used Resource Hacker to edit icons in program before, but
it so long ago, I could never explain how if you paid me.
|

It wouldn't be possible to edit an icon in a system file
due to permissions. What one can do is to make an
icon and then assign that to a shortcut. In addition
to Greenfish, there's IcoFX that I use. I don't know
whether it's still free. IcoFX can also make a multi-image
ICO file. I like to take an image and then paste that into
an icon editor and work from there. It's much easier to
start with something like a reduced-size face than to draw
a face using one pixel at a time.