Port 80 in use

[chamath]

I get the following error. How do I rectify it?

10:21:39 AM [main] Initializing Control Panel
10:21:39 AM [main] Windows Version: Home 64-bit
10:21:39 AM [main] XAMPP Version: 7.4.8
10:21:39 AM [main] Control Panel Version: 3.2.4 [ Compiled: Jun 5th 2019 ]
10:21:39 AM [main] Running with Administrator rights - good!
10:21:39 AM [main] XAMPP Installation Directory: "c:\xampp\"
10:21:39 AM [main] Checking for prerequisites
10:21:41 AM [main] All prerequisites found
10:21:41 AM [main] Initializing Modules
10:21:41 AM [Apache] Problem detected!
10:21:41 AM [Apache] Port 80 in use by "Unable to open process" with PID 4!
10:21:41 AM [Apache] Apache WILL NOT start without the configured ports free!
10:21:41 AM [Apache] You need to uninstall/disable/reconfigure the blocking application
10:21:41 AM [Apache] or reconfigure Apache and the Control Panel to listen on a different port[/color]
10:21:41 AM [mysql] XAMPP MySQL is already running on port 3306
10:21:41 AM [filezilla] XAMPP FileZilla is already running on port 21
10:21:41 AM [filezilla] XAMPP FileZilla is already running on port 14147
10:21:41 AM [main] Starting Check-Timer
10:21:41 AM [main] Control Panel Ready

[Altrea]

We made a sticky out of it:
[Q&A] solving Port 80 in use by PID 4 (http.sys) issue