I enabled IIS 7 on one of my Windows 7 box. When I click start the default site, it always give me error. Said something wrong of the setting. Only when I change the binding port to other than 80, it works.
So, I think port 80 is occupied by other program.
I google it and find the way to point it out.
1) Command line.
So it is clear that Skype use Port 80
Uncheck the check mark to disable it.
It works. The site on IIS 7 can use port 80 right now.