First stop IIS from startmenu by typing IIS manager,
Edit c:/wamp/wampmanager.tpl
file so the WAMP menu points to localhost:80
.
Find http://localhost
and change it to htttp://localhost:80
also, if you think something else has already grabbed port 80, that is why its not working..,then,
Run
wampmanager->Apache->Service->Test port 80
This will launch a command window and tell you what is using port 80.
Whatever it is, will need to be re-configured to use another port or for example if its IIS and you dont use IIS it should be un-installed.
Further you can use 'net stop'
command to stop desired service.