A virtual directory is a friendly name, or alias, for a physical directory on your server that does not reside in the home directory. For example, if you create a virtual directory called "images" from a folder anywhere on your server, the contents of that folder will appear at http://www.domainname.com/images/ even though they are not physically located in the images/ subfolder of your web site's root folder.
1 ) Open Web Site Properties page
2 ) Select Virtual Dirs tab and click Create Directory button
3 ) Add Virtual Directory page will open
4 ) In the Directory Name box, type a name for the virtual directory.
5 ) In the Folder box, type or browse to the physical directory in which the virtual directory resides.
6) Finally, click Create Directory button. Virtual Directory Properties page will open