Xampp Server - Can't run Apache Server

Someone tell me what I'm doing wrong. Log file tells me the certificates are invalid. What next?

3:37:18 PM [main] Initializing Control Panel
3:37:19 PM [main] Windows Version: Pro 32-bit
3:37:19 PM [main] XAMPP Version: 5.6.28
3:37:19 PM [main] Control Panel Version: 3.2.2 [ Compiled: Nov 12th 2015 ]
3:37:19 PM [main] Running with Administrator rights - good!
3:37:19 PM [main] XAMPP Installation Directory: "c:\xampp\"
3:37:19 PM [main] Checking for prerequisites
3:37:26 PM [main] All prerequisites found
3:37:26 PM [main] Initializing Modules
3:37:26 PM [Apache] Problem detected!
3:37:26 PM [Apache] Port 80 in use by "Unable to open process" with PID 4!
3:37:26 PM [Apache] Apache WILL NOT start without the configured ports free!
3:37:26 PM [Apache] You need to uninstall/disable/reconfigure the blocking application
3:37:26 PM [Apache] or reconfigure Apache and the Control Panel to listen on a different port
3:37:26 PM [main] Starting Check-Timer
3:37:26 PM [main] Control Panel Ready
3:37:48 PM [Apache] Problem detected!
3:37:48 PM [Apache] Port 80 in use by "Unable to open process" with PID 4!
3:37:48 PM [Apache] Apache WILL NOT start without the configured ports free!
3:37:48 PM [Apache] You need to uninstall/disable/reconfigure the blocking application
3:37:48 PM [Apache] or reconfigure Apache and the Control Panel to listen on a different port
3:37:48 PM [Apache] Attempting to start Apache app...
3:37:49 PM [mysql] Attempting to start MySQL app...
3:38:00 PM [filezilla] Attempting to start FileZilla app...
3:38:01 PM [mysql] Status change detected: running
3:38:01 PM [filezilla] Status change detected: running
3:38:38 PM [main] Executing "c:\xampp\apache"
3:40:09 PM [Apache] Checking default ports...
3:40:09 PM [Apache] Attempting to start Apache app...
3:40:09 PM [Apache] Executing "c:\xampp\apache\bin\httpd.exe"
3:40:09 PM [Apache] Return code: 0
3:40:10 PM [Apache] Status change detected: running
3:40:11 PM [Apache] Status change detected: stopped
3:40:11 PM [Apache] Error: Apache shutdown unexpectedly.
3:40:11 PM [Apache] This may be due to a blocked port, missing dependencies,
3:40:11 PM [Apache] improper privileges, a crash, or a shutdown by another method.
3:40:11 PM [Apache] Press the Logs button to view error logs and check
3:40:11 PM [Apache] the Windows Event Viewer for more clues
3:40:11 PM [Apache] If you need more help, copy and post this
3:40:11 PM [Apache] entire log window on the forums
3:40:24 PM [main] Executing "c:\xampp\apache\logs"
3:41:18 PM [main] Executing "c:\xampp\apache"
3:42:52 PM [Apache] Checking default ports...
3:42:52 PM [Apache] Attempting to start Apache app...
3:42:52 PM [Apache] Executing "c:\xampp\apache\bin\httpd.exe"
3:42:52 PM [Apache] Return code: 0
3:42:52 PM [Apache] Status change detected: running
3:42:53 PM [Apache] Status change detected: stopped
3:42:53 PM [Apache] Error: Apache shutdown unexpectedly.
3:42:53 PM [Apache] This may be due to a blocked port, missing dependencies,
3:42:53 PM [Apache] improper privileges, a crash, or a shutdown by another method.
3:42:53 PM [Apache] Press the Logs button to view error logs and check
3:42:53 PM [Apache] the Windows Event Viewer for more clues
3:42:53 PM [Apache] If you need more help, copy and post this
3:42:53 PM [Apache] entire log window on the forums
3:43:00 PM [main] Executing "c:\xampp\apache"
3:44:30 PM [Apache] Checking default ports...
3:44:30 PM [Apache] Portblocker Detected: System
3:44:30 PM [Apache] Checking for App: c:\xampp\apache\bin\httpd.exe
3:44:30 PM [Apache] Portblocker Path: Unable to open process
3:44:30 PM [Apache] Portblocker Service Path:
3:44:30 PM [Apache] Problem detected!
3:44:30 PM [Apache] Port 80 in use by "Unable to open process" with PID 4!
3:44:30 PM [Apache] Apache WILL NOT start without the configured ports free!
3:44:30 PM [Apache] You need to uninstall/disable/reconfigure the blocking application
3:44:30 PM [Apache] or reconfigure Apache and the Control Panel to listen on a different port
3:44:30 PM [Apache] Attempting to start Apache app...
3:44:30 PM [Apache] Executing "c:\xampp\apache\bin\httpd.exe"
3:44:30 PM [Apache] Return code: 0
3:44:30 PM [Apache] Status change detected: running
3:44:31 PM [Apache] Status change detected: stopped
3:44:31 PM [Apache] Error: Apache shutdown unexpectedly.
3:44:31 PM [Apache] This may be due to a blocked port, missing dependencies,
3:44:31 PM [Apache] improper privileges, a crash, or a shutdown by another method.
3:44:31 PM [Apache] Press the Logs button to view error logs and check
3:44:31 PM [Apache] the Windows Event Viewer for more clues
3:44:31 PM [Apache] If you need more help, copy and post this
3:44:31 PM [Apache] entire log window on the forums
3:44:38 PM [filezilla] Attempting to stop FileZilla app...
3:44:38 PM [filezilla] Executing "c:\xampp\filezillaftp\filezillaserver.exe -compat -stop"
3:44:38 PM [filezilla] Return code: 0
3:44:38 PM [filezilla] Status change detected: stopped
3:44:41 PM [Apache] Checking default ports...
3:44:41 PM [Apache] Portblocker Detected: System
3:44:41 PM [Apache] Checking for App: c:\xampp\apache\bin\httpd.exe
3:44:41 PM [Apache] Portblocker Path: Unable to open process
3:44:41 PM [Apache] Portblocker Service Path:
3:44:41 PM [Apache] Problem detected!
3:44:41 PM [Apache] Port 80 in use by "Unable to open process" with PID 4!
3:44:41 PM [Apache] Apache WILL NOT start without the configured ports free!
3:44:41 PM [Apache] You need to uninstall/disable/reconfigure the blocking application
3:44:41 PM [Apache] or reconfigure Apache and the Control Panel to listen on a different port
3:44:41 PM [Apache] Attempting to start Apache app...
3:44:41 PM [Apache] Executing "c:\xampp\apache\bin\httpd.exe"
3:44:41 PM [Apache] Return code: 0
3:44:41 PM [Apache] Status change detected: running
3:44:42 PM [Apache] Status change detected: stopped
3:44:42 PM [Apache] Error: Apache shutdown unexpectedly.
3:44:42 PM [Apache] This may be due to a blocked port, missing dependencies,
3:44:42 PM [Apache] improper privileges, a crash, or a shutdown by another method.
3:44:42 PM [Apache] Press the Logs button to view error logs and check
3:44:42 PM [Apache] the Windows Event Viewer for more clues
3:44:42 PM [Apache] If you need more help, copy and post this
3:44:42 PM [Apache] entire log window on the forums
3:45:10 PM [main] Executing "c:\xampp\apache"
3:45:42 PM [main] Executing "c:\xampp\apache"
3:47:30 PM [main] Executing "services.msc"

 

Have you got Skype running? Skype is a common culprit for the use of port 80