Apache vs Skype
I installed XAMPP so that I could do my Web Apps coursework. However, Apache wouldn't start - it launched, but then quit immediately. I did a quick Google and someone pointed out that Skype grabs port 80 on startup, preventing Apache from using it. When I quit Skype, Apache started up just fine. A little exploration turned up a Skype setting to stop it doing this, located at Tools -> Options -> General -> Set Connection Parameters and Proxies -> Use port 80 and 443 as alternatives for incoming connections. Now Apache and Skype co-exist just fine.