Photokey greenscreen software is specifically designed to remove greenscreen or bluescreen backgrounds from photos. Those are the only colors it works with. Trying to remove a background of any color other than green or blue is beyond the scope of the program's abilities.
If you have photos with white background that you are trying to remove, You'll need to use other software; perhaps GIMP? It is free, and the wand tool or select color range tool should make selecting the white areas relatively quick and easy.