PORT 5432 ERROR

I am receiving an error when I enter the server port number to listen to—installed on all available versions, both 32-bit and 64-bit when applicable, even the latest version, 15.3 x64 for Windows. I downloaded the latest version as an example, and as I was told, I used the 5432 port as the default port needed. I get a pop-up afterward saying, "Warning: The specified port number is not available. Please enter a different port number," than roadblocks at entering the default port number. I found port 5434 available though it locks at a loading screen "loading server Postgre version 7.4. Version 10 works on port 5434 though the server list tree spins eternally.