I am new to DNN. I am able to create and view pages of the default portal but creating a new parent portal doesn’t work.
When I create new portal(parent) , it does shows up in the 'host'-> portal list but when I browse it gives an error 'Internet Explorer cannot display the webpage'.
If I add the 'host name' manually in 'C:\Windows\System32\drivers\etc\hosts' it gives me an error 'Domain Name Does Not Exist In The Database'.
Will highly appreciate if someone could guide what I am doing wrong.

Thanks, works now :)

I spent an inordinate amount of time on this so i'll add more for the benefit of others. If you are hosting on GoDaddy's web hosting, there are several things that you need to do in order to support multiple Parent Portals in a single DNN instance/install (I'm working with 5.6):
1) Upgrade your hosting account to at least Deluxe level so that you can configure subfolders through the GD Hosting Control Center | Settings | Domain Management | Add Domain function. Yes, your domain needs to point to the DNN install before you add a parent portal.
2) Add the subfolder in the Add Domain where your DNN is installed ("/dnn" in my case).
3) Log into DNN as the Host admi and go to Host | Sites page.
4) Add New Portal. The Parent option is selected by default.
5) Put the name of your domain into the Portal Alias field. In DNN 5.6, this doesn't create an alias, but informs the DNN code of your domain name. Select a template and enter the credentials for this sites administrator.
6) AFTER the portal is created, you need to go back through Host | Sites and edit the portal you just created.
7) Add a manual alias that points to the "newParentPortalDomain.xxx/dnn". Adding this alias doesn't intuitively seem correct, however, it informs the DNN code of the pathname configured through GD's Domain Management so that the DNN code can parse and rewrite the URLs correctly in order to maintain your newParentPortalDomain.xxx in the URL, navigate to the correct pages in your new site, not default to the PortalID0, PortalID1 or any other portal hosted by this instance.

Here is an archived forum post that helped me in deriving this approach through much trial and errorr:
http://seablick.com/blog/55/creating-a-dnn-parent-portal.aspx

now i need to dig into content reuse across parent and child portals. Site templates can be used to replicate content, but I need a way to change some modules and reuse them across several different sites managed by the same DNN instance.