How to convert ART file format? [Pictures]?

When you download images from the net or Aol the files may be saved as i.e. myfile.art or myfile.bmp or sometimes the file maybe saved as myfile.jpg or myfile.gif but for some reason you may not be able to open the file in a graphics program. This is because they are .art formatted files even if the file extension reads .jpg .gif and most graphic applications can not handle this .art file format, America Online for example utilizes graphics compression software that speeds up the delivery of web pages to it's members by compressing images and various multimedia applications. Images that are BMP, GIF or JPG are converted into the proprietary Johnson-Grace image format .ART.
===================
Pictures of Australia