I had the following error message Port 80 in use by "Unable to open process" with PID 4! Apache WILL NOT start without the configured ports free! You need to uninstall/disable/reconfigure the blocking application or reconfigure Apache and the Control Panel to listen on a different port Starting Check-Timer Control Panel Ready
opened the httpd.conf and changed the listen port from 80 to 1234 in both places
Listen 1234
Then go to Config for the xampp control panel and go to service and port setting and changed the port from 80 to 1234
That worked.