I got an interesting situation recently:
I tried to start-up the default site on the IIS and it exited with error - another process is listening on that port (or something like that). The point is that some program was already listening on port 80 before I start-up the IIS.
A very surprising for me, because the Apache is running on another linux machine and has nothing to do with the IIS.
Fortunately there is a very very useful program called TcpView which actually does exactly the same as the command line: netstat -anb but in graphical interface.
So, what is the surprice:
Somebody, pleas tell me what does the SKYPE needs a port 80 and 443 for ???