This is very simple but I just installed the latest version of XAMPP. I ran the control panel and changed the listening port from 80. I ran Apache and it showed up as running, puts out a pid in the control panel then terminates in about a quarter second. I checked for logs, there were absolutely none. I ended up running httpd from the command prompt and it told me port 80 was in use and died. Again no logs. The httpd.conf hadn't been changed by the control panel so still went to 80. However, that does not change the fact that a few messages should have been logged in error or system logs.
Was anything logged in event viewer?