David,
.JPG files are 24 bit images that have been compressed in to JPEG
format… they don't need to be de-archived. They do, however, require a
viewer or program that understands the JPEG format. If all you want to do
is view the image, VIEWTEK 1.05 (available here in the AmigaArts library)
will load and view them just fine. If you want to manipulate the image,
all of the top processing packages (ADPRO-IMAGE F/X-IMAGEMASTER) handle
JPEG's very well.