I suggest using the .png format to save your rendered image. It's what is known as a "lossless" format and doesn't compress the image so the quality remains high. Also if your graphic program supports transparent alpha channels the image will not have a background when you open it inside PSP.

If you save as a .tiff you will need to apply the image to itself as a mask in order to get rid of the background.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi