If the PostgreSQL service is not listed in services.msc then it isn't currently installed so I recommend manually downloading and installing PostgreSQL v9.3 again
from here. When installing use "dbpass" (no quotes) for the PostgreSQL password which is what PokerTracker 4 uses by default. If you receive confirmation that the install was successful then at the end of the PostgreSQL install remove the check mark from the "Stackbuilder" option, click "Finish" and try starting PokerTracker 4 again. If the PostgreSQL install did not complete successfully send us ths file in a
Support Ticket:
C:\Users\{Windows Login}\AppData\Local\Temp\install-postgresql.log