Icons are often required to be in the .icon format, a format that many people are not familiar with and that many programs don't have the ability to create. If you need to create a .ico file for an icon and all you have are images in .png, .jpg, or gif, there is a free on-line conversion tool at http://www.converticon.com/. It uses a Flash plug-in that allows you to upload images in "normal" image formats and it'll convert them into the .ico icon image format.