Apache: Only one usage of each socket address is normally permitted: make_sock could not bind to address 0.0.0.0:80 no listening sockets available, shutting down

I got this problem with my Apache server this morning:

Only one usage of each socket address *  is normally permitted. : make_sock could not bind to address 0.0.0.0:80 no listening sockets available, shutting down 

Unable to open logs 

Note the errors or messages, above, and press the key to exit.

It turned out that my newly installed Skype should be responsible for this debacle.So I fixed the problem by changing the Skype configuration.

Why should Skype eavesdrop on the default 80 port and break all the other applications is a mystery to me. And although the problem is there for at least one and a half years, Skype still has no intention to fix this, even though the fix is as simple as disabling a checkbox.