Well have tried all the tips posted above except for,
( Or, for more detailed GUI editing:
http://gimp.org/ )
and they all failed to convert .art files to jpeg.
BMP coverts easily to jpeg.
It seems that .art format was a joint venture between MS/AOL years ago.
As Cashanova pointed out in that: MS Security Bulletin
Due to "A remote code execution vulnerability exists in the way AOL ART images are handled", the AOL .ART file filter has been disabled to protect your system from this threat, which is deemed to be "High Risk" by Microsoft.
I think MS is blocking them files from being opened by IE anymore.
Even ACDSee Pro Photo Manager that claims it can open the .art file extension couldn't open or convert .art files.