Sometimes it's needed to delete the existing PostgreSQL database, especially if a different major version was installed at first by mistake (for example, 9.6 in place of the supported 9.4). Then it's absolutely necessary to ensure the database is fully deleted and there is no db ghosts.
The proper way to uninstall is to go to the postgresql server installation directory and find one uninstall-postgresql file. Double click on the Uninstall-postgresql file to run the un-installer- it will
In case the uninstall wasn't performed correctly, below are the manual steps to clean it up. One sign of existing "ghost" db, is randomly seeing a second PostgreSQL server in the pgAdmin III or experiencing "error"-less problems when running the ThingWorx installation scripts.
To uninstall manually,in this example we will use 9.6 as the version to delete - please replace with your own where needed:
Remove the postgresql server installation directory. (rd /s /q "C:\Program Files\PostgreSQL\9.6") Assuming default location.
Delete the user 'postgres' (net user postgres /delete)
Remove the Registry entries. (HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-9.6) and (HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Services\postgresql-9.6)
Remove the postgresql-9.6 service. (sc delete postgresql-9.6)