I was recently stuck trying to figure out why my local apache instance was not starting. I changed the port that it listened to from 80 to 8080 to 8001, and no luck. After running “netstat -ano” from the command line, I could see an application was listening to port 443, which is required for https. After enabling the PID column in Task Manager (View->Select Columns…), I was able to see which application corresponded to the PID that netstat was reporting, and it turned out to be Skype. After exitting Skype, I tried to start apache again and it worked! So just something to keep in mind, not just port 80 but port 443 have to be open and Skype listens on that port.