Because they both web server and conflict each other, shut down your iis, your apache will work. Then, you can open httpd.conf in wamp/apache2/conf and change listen 80 to something else like listen 81 for example so both can work, but remember, you will run into other problems later since they're conflicted. Restart wampserver after any change.
They both use port 80, you have to change port for either one. Also, disable windows firewall, enable port 80 in 3-party firewall such as Norton, McAfee, and enable portforward in router, too.