1. Browse to: C:\Windows\System32\drivers\etc and open the file called 'hosts' in any text editor. You should see 1 or more lines that have an ip address, then the hostname. Eg:
Add a new line to it with something like:
Then save and close the file.
2. Open up httpd.conf from the Wamp tray icon menu and scroll down until you find:
And un-comment it by removing the '#' from the start of the line.
3. Open up: C:\wamp\bin\apache\apache2.2.6\conf\extra\httpd-vhosts.conf. You should find 2 demo virtual hosts in there - dummy-host.localhost - and - dummy-host2.localhost - delete the second one (the entire block), then edit the first one to your needs. Just change "dummy-host.localhost" to "test.localhost" (or whatever you called it in the Hosts file, then adjust the www / log paths as needed.
And finally, restart Apache and all should be fine. If you run into problems after the restart, check the Apache error log. You may also need to restart your PC for Windows to pickup the changes you made to the Hosts file.