Having been asked by a friend if I have a certain photo in my collection- and please could he have a copy. I found the only one presentable was of him and his now departed friend was in a group. So I cropped it out and did the magic of Paint Shop. But it is a huge enlargement and now a little noisy. PSP did its best and I have also 'Picture cooler2' which did a little but not much. Is there an interpolation software out there that will work the miracles- Free of course.
I'm not sure what options you have on PSP, but on PS CS2 there is an option when increasing size to select Bicubic Smoother, or Bicubic Sharper. Both setting will do a reasonable job. However degredation will always set in when increasing an image size.
One of the better programs for upsizing is Genuine Fractals, but at a price.
Photofiltre is a good program,but will not do what you want