You will either have to install the app that created those or look at viewers such as listed at http://alternativeto.net/software/xnview/
http://www.irfanview.com/ does not list this type so use the above link for others.
http://en.wikipedia.org/wiki/ART_image_file_format shows where they came from and my advice is to take AOL's advice and turn off the compression.
I am trying to open ART files, epp and others and I can't. I keep getting the message a suitable graphic importer could not be found.