If you have another photo editing tool, it may well work better for this than Paint. With Paint, you'll need to use Stretch/Skew instead of Attributes, and change the number for percentage in the boxes for Horizontal and Vertical. To keep maintain the original aspect ratio, use the same percentage in both boxes. You'll have to experiment to try to get your image to 80x80, if you need that exact size.
If you have no other photo editing software, you might download the free
IrfanView and try it.