about Sharepoint Portal Server 2003

[Raj]

1. We have two options to extend a virtual server :
a . Windows sharepoint services-->Virtual Server Configuration
--->Extend or upgrade virtual
server
b. SharePoint Portal Server Central Administration-->Portal Site
and Virtual Server
Configuration-->Create a portal site

so plz, let us know, the differences between above two processes.


2. We have extended the virtual server through:
Windows sharepoint services-->Virtual Server Configuration
--->Extend or upgrade virtual
server .

But we are not able to create a portal site for this extended
virtual server. Why?