Tried to install a local Apache this morning and couldn’t get it to start. Turned out Skype was the problem. Matt apparently encountered this years ago, but I never really started using Skype until lately.
Anyway, it still happens. But there’s a simple fix.
Go to the Tools->Options menu. In there, find the Advanced->Connections tab. Turn off the option to use port 80 and 443. These are there to allow Skype to try to get through firewalls. They also, incidentally, block Apache from starting since it can’t grab the port it wants.
Just a heads up in case anybody else encounters the problem.