Sorry I dont have Photostory but, for most all Magix programs, project files are stored in a folder with the name of the program eg C:\Document and settings\ ... \Magix MEP 14+ for this video editor program. The exact path depends on your operating system eg Win XP or Win 7 etc.
If you still have your original program installed open an old show and then when you start a 'Save as' check exactly where it is going. Alternately do an Windows Explorer search.