Depends on what server you're using. For IIS, you can create a virtual site, and make sure you specify the same IP address and the Host Name.
For Apache, simply add a
<VirtualHost {my IP}>
DocumentRoot /fataldesigns.com/md
ServerName xyz.fataldesigns.com
</VirtualHost>
Take a look at
http://www.apache.org/docs/vhosts/ for more info.