Skype has some conflicts with XAMPP when running Apache. By default Apache and Skype both uses Port 80 or Port 443.
It throw a error message as show in image below.
The solution of this issue is , either make Apache use other port or make Skype use other port than 80 or 443.
To make Skype use other port. Go to Tools -> Options -> Advance -> Connection
and uncheck the box shown below. Restart Skype and XAMPP. There should not be any issue now.