This has always been an issue when using Xampp - as it requires Port 80 to be free to operate. Many common programs use Port 80 - e.g. Skype, is the most common conflict.
You can (a) shut the Program down while you use Xampp, or as in the case of Skype, the advanced settings can nominate not use Port 80, and 443 ... and this can free up the Port for Xamp.
You can use CMD (command prompt administrator) and type in netstat -aon to see which programs/ports are using port 80 and use task manager to close them.
I should mention that Hackers are now using these same Ports when they have broken into your wireless Router - either via your (aged) Mobile Phone or your (aged) Wireless Device ... or a modern one that is not using device pairing meticulously.