I don’t know how many people use an image to icon converter (free of course) at some time or another, but I am one and have tried many, either online or downloadable. SimplyIcon which can be found at
http://www.smoothdraw.com/simplyicon" onclick="window.open(this.href);return false; is a portable downloadable programme and is the easiest of all those I have tried.
The following is from the website:
Simply create windows icon files (.ICO format) by drag-and-drop images on to this program. Actually I wrote this program because I need a simple tool to generate icons, but I haven't found any decent free ones. This program generates down-sampled 32x32, 24x24 and 16x16 levels automatically. It will also generate the 128x128 level if your source image is equal to or larger than 128x128.
System Requirement: .NET Framework 2.0
Hope someone else might find it useful.