Conflict between XAMPP and Skype
If you are not able to start Apache web server in XAMPP, in the most of cases the main cause is that some other application uses the same port (default is 80). That is the reason why we advise changing Apache port in XAMPP. And at the first place among all applications that use port 80, except another web server, is Skype.
XAMPP is a free and open source cross-platform web server solution stack package, consisting mainly of the Apache HTTP Server, MySQL database, and interpreters for scripts written in the PHP and Perl programming languages.
The program is released under the terms of the GNU General Public License and acts as a free web server capable of serving dynamic pages. XAMPP is available for Microsoft Windows, Linux, Solaris, and Mac OS X, and is mainly used for web development projects. This software is useful while you are creating dynamic webpages using programming languages like PHP, JSP, Servlets.
How to fix conflict with the Skype port
So it could cause port conflict and here are steps how to fix conflict between XAMPP and Skype, i.e. how to disable the usage of port 80 in Skype in order to release it for Apache web server in XAMPP:
1) Start Skype
2) Go to Tools > Options > Connections
3) Uncheck the option "Use of Port 80 as an alternative port"