The quickest solution, if you are willing to lose your old database, is to completely uninstall PostgreSQL, delete the C:\Program Files\PostgreSQL\ directory, then reinstall. You can find a more detailed guide available
here. If you have not changed any other default settings you will be able to reimport the hands that were in the old database by running a manual import on the C:\Program Files\PokerTracker 3\Processed directory.