How to Change IIS Port in Windows 7
You need to change Internet Information Services (IIS) Port (Change IIS Port), if you are having XAMPP installed on your PC. Usually Port 80 was used by IIS, when you install XAMPP Port 80 will be assigned to APACHE server. So that you will not be able to access your IIS Web Sites.
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In order to access your IIS Websites, you need to change the Port of Default Web Site in IIS. By default IIS port value is 80, Now change it to 81.
How to do this?
#1. In Start menu Search option, type: IIS and click Internet Information Services Manager or simply do a run command: inetmgr .
#2. Under Connections, You’ll see your PC name click on it to expand the list. Now you can see “Sites” click on it to expand.
#3. Under Sites you can see Default Web Site, right click on it and Select EDIT BINDINGS.
#4. Edit HTTP binding port from 80 to 81.
#5. Open your browser and type: //localhost:81/yoursite. You should be able to access your local sites without any problems.
source: http://www.gadgetcage.org/how-to-change-iis-port-in-windows-7/3457/