Software to change image formats?

Hi; I want my PC to be a part of my style and persona. Not the same old boring folder icons that everyone has. In the endeavor to do so I want to be able to use jpeg, gif, Tif etc.. images and change them to ico format cause that is the only format the folder image can accept. Is there a freely available software which I can use to convert any image format to an icon? I am looking for something like the dummies way out :)