Thanks for your interest in Songsmith, and sorry you're having trouble installing it.
Firstly, can you confirm that you downloaded Songsmith from here:
http://songsmith.ms/download.html
That's the current version. If you downloaded it from anywhere else, please download it from our site and try installing it again.
If it still doesn't work, can you let us know what version of Windows you're using?
Thanks!
-Dan from the Songsmith team