Easy way to create a .ICO icon file

To create a quick .ico file (windows icon format), use this excellent free online tool here: http://converticon.com/

The utility supports GIF, PNG, JPEG and other file types.
Once you click 'Get Started' don't forget to choose your filetype.

It exports to various default sizes.

More info on the .ICO format here: http://en.wikipedia.org/wiki/ICO_(file_format)