There can be different cases: 

1. a) You need to install Visual C++ Redistributable for Visual Studio 2015 x86.
   b) After that, reboot your computer and try again. If the apache is still not 
    starting, run the XAMPP control panel as administrator.

2. In case that you're using Skype, make sure the tick allowing it to use ports 
80 and 443 is not selected. End Skype task and remove skype from start up.