That's odd. When you type in localhost in your browser, do you get an empty page or a page telling you it can't connect?
Could there be another HTTP server running on the machine? IIS, for example?
Try changing the port your Apache server runs on. You can do that by opening the file
"C:\wamp\bin\apache\Apache2.2.11\conf\httpd.co nf" in notepad and changing the number in the following line to something else. I'd recommend something around 50000, to avoid conflicts.
Then try to start the server.