JASC renames file type?
I doubt if it changed the actual filetype at all. My jpegs appear as "Irfanview JPG files" - but that's only because I selected Irfanview as my default handler for jpegs. If I change the default handler, the file type descriptions will change, but the files won't be affected.
We can't have applications spontaneously converting our files all over the place - that way madness lies.