This elegant solution will enable you to create a configuration for subdomain in the localhost (e.g. http://mail.localhost) that can be carried on to production.
I admit I am a little late into web page development, and I stumble into what almost all newbie face: you can’t load XAMPP after you load Skype, because they both use the same port 80 (http) and 443 (https) to listen to incoming connection. After a quick search in the internet, I found out that the solution was already up and around since 2009.
In short, the solution is: In Skype go to Tools > Options and click on the Advanced tab, sub-tabs open up, click on Connection. Skype’s default port is a random value with 4 or 5 digits and also relies on ports 80 & 443 as alternatives. Just unchecked the “use port 80 and 443 as alternatives for incoming connection”. This will be useful if you’re working behind a tight firewall. But you aren’t, chance are Skype will be working just fine. But if you really have some problem, then I’d suggest you to use port 443 for incoming connection, rather than the random 4 or 5 digits. But then, you won’t be able to use port 443 for testing. But oh why bother if you aren’t going to use it in development anyways, because XAMPP usually used for development environment, not production environment. In the production server, you usually won’t install Skype there.