You can change the port that the Internet Information Services (IIS) will listen to. This can be useful when you are trying to run multiple web servers on the same computer.
1. Open the Internet Information Services (IIS) Manager.
2. Select the Default Web Site that you wish to configure.
3. In the Actions panel, click Bindings. The Site Bindings dialog displays.
4. Click Add to add a new site binding or Edit to change an existing binding. The following example assigns port 81 to http.
5. Click OK to apply the changes.
See this Microsoft article for more: http://support.microsoft.com/kb/149605