Click on the WAMP server icon and from the menu under Config Files select
httpd.conf. A long text file will open up in notepad. In this file scroll
down to the line that reads
Port 80 and change this to read
Save the file and close notepad. Once again click on the wamp server icon and
select restart all services. One more change needs to be made before we are
done. In Windows Explorer find the location where WAMP server was installed
which is by Default
Update : On a newer version of WAMP, click the WAMP server icon > Apache >
httpd.conf, then change the line
Listen 80 to
Listen 8080 or any port you want.
Update： On 3.1.6 version of WAMP ， right click on the wamp server icon in the taskbar ，select “tools”-> “Port used by Apache:80” -> “use a port other than 80”, an input box will pop up , input a new port in it，click confirm button , then restart wamp .