The process cannot access the file because it is being used by another process" error message when you try to start a Web site in the Internet Information Services

The WWW Publishing Service, did not register the URL prefix http://x.x.x.x:80/ for Default Web Site.

A) Symptoms

1) On System log Event: 1004 Source: IIS-W3SVC Error received when trying to start the stopped Default web site:
2) The process cannot access the file because it is being used by another process. (Exception from HRESULT: 0×80070020)

First of all we need to verify nothing else is use the x.x.x.x:80 IP address and port.
Running command prompt with Admin rights and type: netstat -ano |findstr 80
Verify no other process is listening on the x.x.x.x IP and port 80.
Check if something is listening on port 80 when the Default web site is stopped.
If nothing is listening on port 80 go on.

B) Resolve
Running command prompt with Admin rights and type:

1) net stop http
2) In regedit browse to: 
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters\ListenOnlyList
3) If an IP address is listed in the ListenOnly List, change the IP address to 0.0.0.0
4) From administrative command prompt type: net start http

From the services applet, restart the World Wide Web Publishing Service

More info: Link