Error: Apache shutdown unexpectedly.

[pokhrelcp]

My XAMPP Control Panel showing following result while starting Apache. What should I do to run Apache?
12:08:14 [Apache] Error: Apache shutdown unexpectedly.
12:08:14 [Apache] This may be due to a blocked port, missing dependencies,
12:08:14 [Apache] improper privileges, a crash, or a shutdown by another method.
12:08:14 [Apache] Press the Logs button to view error logs and check
12:08:14 [Apache] the Windows Event Viewer for more clues
12:08:14 [Apache] If you need more help, copy and post this
12:08:14 [Apache] entire log window on the forums

[pokhrelcp]

11:50:09 [main] Initializing Control Panel
11:50:09 [main] Windows Version: Home 64-bit
11:50:09 [main] XAMPP Version: 5.6.23
11:50:09 [main] Control Panel Version: 3.2.2 [ Compiled: Nov 12th 2015 ]
11:50:09 [main] You are not running with administrator rights! This will work for
11:50:09 [main] most application stuff but whenever you do something with services
11:50:09 [main] there will be a security dialogue or things will break! So think
11:50:09 [main] about running this application with administrator rights!
11:50:09 [main] XAMPP Installation Directory: "d:\xampp\"
11:50:09 [main] Checking for prerequisites
11:50:09 [main] All prerequisites found
11:50:09 [main] Initializing Modules
11:50:09 [Apache] Problem detected!
11:50:09 [Apache] Port 80 in use by "Unable to open process" with PID 4!
11:50:09 [Apache] Apache WILL NOT start without the configured ports free!
11:50:09 [Apache] You need to uninstall/disable/reconfigure the blocking application
11:50:09 [Apache] or reconfigure Apache and the Control Panel to listen on a different port
11:50:10 [main] Enabling autostart for module "Apache"
11:50:10 [main] Enabling autostart for module "MySQL"
11:50:10 [main] Starting Check-Timer
11:50:10 [main] Control Panel Ready
11:50:10 [Apache] Autostart active: starting...
11:50:10 [Apache] Problem detected!
11:50:10 [Apache] Port 80 in use by "Unable to open process" with PID 4!
11:50:10 [Apache] Apache WILL NOT start without the configured ports free!
11:50:10 [Apache] You need to uninstall/disable/reconfigure the blocking application
11:50:10 [Apache] or reconfigure Apache and the Control Panel to listen on a different port
11:50:10 [Apache] Attempting to start Apache app...
11:50:10 [mysql] Autostart active: starting...
11:50:10 [mysql] Attempting to start MySQL app...
11:50:15 [Apache] Status change detected: running
11:50:15 [mysql] Status change detected: running
11:50:17 [Apache] Status change detected: stopped
11:50:17 [Apache] Error: Apache shutdown unexpectedly.
11:50:17 [Apache] This may be due to a blocked port, missing dependencies,
11:50:17 [Apache] improper privileges, a crash, or a shutdown by another method.
11:50:17 [Apache] Press the Logs button to view error logs and check
11:50:17 [Apache] the Windows Event Viewer for more clues
11:50:17 [Apache] If you need more help, copy and post this
11:50:17 [Apache] entire log window on the forums
11:50:26 [Apache] Problem detected!
11:50:26 [Apache] Port 80 in use by "Unable to open process" with PID 4!
11:50:26 [Apache] Apache WILL NOT start without the configured ports free!
11:50:26 [Apache] You need to uninstall/disable/reconfigure the blocking application
11:50:26 [Apache] or reconfigure Apache and the Control Panel to listen on a different port
11:50:26 [Apache] Attempting to start Apache app...
11:50:26 [Apache] Status change detected: running
11:50:27 [Apache] Status change detected: stopped
11:50:27 [Apache] Error: Apache shutdown unexpectedly.
11:50:27 [Apache] This may be due to a blocked port, missing dependencies,
11:50:27 [Apache] improper privileges, a crash, or a shutdown by another method.
11:50:27 [Apache] Press the Logs button to view error logs and check
11:50:27 [Apache] the Windows Event Viewer for more clues
11:50:27 [Apache] If you need more help, copy and post this
11:50:27 [Apache] entire log window on the forums
12:00:41 [Apache] Problem detected!
12:00:41 [Apache] Port 80 in use by "Unable to open process" with PID 4!
12:00:41 [Apache] Apache WILL NOT start without the configured ports free!
12:00:41 [Apache] You need to uninstall/disable/reconfigure the blocking application
12:00:41 [Apache] or reconfigure Apache and the Control Panel to listen on a different port
12:00:41 [Apache] Attempting to start Apache app...
12:00:41 [Apache] Status change detected: running
12:00:41 [Apache] Status change detected: stopped
12:00:41 [Apache] Error: Apache shutdown unexpectedly.
12:00:41 [Apache] This may be due to a blocked port, missing dependencies,
12:00:41 [Apache] improper privileges, a crash, or a shutdown by another method.
12:00:41 [Apache] Press the Logs button to view error logs and check
12:00:41 [Apache] the Windows Event Viewer for more clues
12:00:41 [Apache] If you need more help, copy and post this
12:00:41 [Apache] entire log window on the forums
12:08:13 [Apache] Problem detected!
12:08:13 [Apache] Port 80 in use by "Unable to open process" with PID 4!
12:08:13 [Apache] Apache WILL NOT start without the configured ports free!
12:08:13 [Apache] You need to uninstall/disable/reconfigure the blocking application
12:08:13 [Apache] or reconfigure Apache and the Control Panel to listen on a different port
12:08:13 [Apache] Attempting to start Apache app...
12:08:13 [Apache] Status change detected: running
12:08:14 [Apache] Status change detected: stopped
12:08:14 [Apache] Error: Apache shutdown unexpectedly.
12:08:14 [Apache] This may be due to a blocked port, missing dependencies,
12:08:14 [Apache] improper privileges, a crash, or a shutdown by another method.
12:08:14 [Apache] Press the Logs button to view error logs and check
12:08:14 [Apache] the Windows Event Viewer for more clues
12:08:14 [Apache] If you need more help, copy and post this
12:08:14 [Apache] entire log window on the forums