1) Stop IIS Server (type inetmgr.exe in run command)
2) Locate httpd.config file (default path is C:\wamp\bin\apache\Apache2.2.21\conf)
3) Locate below lines
and change them with
Save httpd.config file and restart wamp services. You can see that it will be now changed into green color.
Please comment if this post is helpful for you.