Virtual Server with Sharepoint 2003

[netcashin]

I have been working on Sharepoint server 2007 for awhile now, but we have one server running sharepoint 2003. There is a need to create a new portal site on the box with sharepoint 2003. When I go to create the new portal site, it asks for the virtual server.

How do I create a new virtual server that the new portal site can use?

Thanks