This is due to "Data Execution Prevention" settings in Vista. By default this is turned off, but if you have turned it on you can make the following change to fix the error message.
Open System by clicking the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking System. Click Advanced System Settings, if you are asked for an administrator password please enter it. Under Performance click Settings, and click the Data Execution Prevention tab. Now click "Add" and browse to the executable for Portrait Professional, which is usually "C:/Program Files/Portrait Professional/PortraitProfessional.exe" and then click OK.