|If you just enlarge a picture all you are essentially doing is zooming in so what you are seeing is the individual pixels. You can't use Paint to get around this, and I don't think there are any free programs to do it either. Photoshop has an add-on called Genuine Fractals that can do the job but it's around $100, on top of the cost of photoshop.|
EDIT: There is a free graphics program called Irfanview - far more advanced than Paint and I've read that it does do interpolation (which is what you are trying to do - ie fill the gaps between the pixels) of some sort. May be worth a try.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd