Most mac aps can be dragged to the trash. In your case it sounds like the behavior of the mac has changed? Do you keep up with your updates? In any case you would be best served to learn more about the operating system to go into the library to remove the postgre elements that are causing you grief. There is a good book called Mac 911 for Tiger, if you have tiger? It will tell you about the hidden files in the unix underpinnings that are hidden from users.
This is the bigger part of your issue I expect. In any case, since this mac is new I am thinking you are better off re-installing your os and when done go to the apple at the top right corner, click on it and go down to the second choice: software update. Do this several times... by this I mean go back after each restart and do it again until there are no more updates left. You need to do this in any case so everything will run better and more securely...
Good luck. And remember to back up any important files, and any links in your browser as they will all go away... -- Read more at http://www.xtuple.org/phpBB2/viewtopic.php?t=556