On a system running Windows 7, I had installed the program into a folder of my own choosing and had the same problem as Peter Blaise. In case the program was looking for something in its default directory I completely uninstalled the program, then reinstalled it into the default directory. I had un-ticked the 21 day trial box in both installations. After the second installation the program opened without errors.
The program did not tell me that it was a 21 day trial, and in the help menu I clicked on the Premium Version, which brought up a dialogue box in which I could enter the license key. This was all done with administrator rights.
When I tried to run the program without administrator rights it would not open, giving an error message that it could not find a file which was in the administrator’s user directory,
C:\Users\Administrator\AppData\Local\Photo Pos Pro 3\AppData
When I copied the contents of the Administrator’s directory, including sub-folders, into my own non-administrator directory
C:\Users\Non-Administrator\AppData\Local\Photo Pos Pro 3\AppData
the program opened correctly. This has taken a lot of time so I haven’t tried to do anything with the program yet to know if it does what it is supposed to do.