Don't know why Skype has to block port:80, but it apparently does, which prevents XAMPP, or any other instance of Apache/2 to run. This snippet from ApacheFriends helped isolate the probem.
(7) You have other software, such as the Internet Telephone "SKYPE" which also blocks the port 80. (thanks Peter! ) However, one can change the SKYPE port: Actions -- > Options --> Connection. Here remove the check mark at "Port 80" for an alternate port. Restart Skype and also it should work.