Apache has VirtualHost directive, so you serve say,
yahoo.com requests from a directory
yahoo you've, say, in
/wwwroot. You don't need register a domain, you are installing Apache 2 to your local machine. Just enter localhost for server name or domain and postmaster@localhost for e-mail.
What's really important is you need set
http.conf correctly. And change Web publishing service of IIS to port, say, 8080, if you install Apache for port 80. You usually, use PHP, Perl and MySQL installation with Apache.
Cheer up :)
http://www.mediasworks.org/scripts/