Hi Marcus,
As it happens the next issue for Jan covers portals, aliases, etc.
This is the method I use for adding a second parent portal to a localhost installation in win XP pro.
I have IIS installed on my localhost installation, so perhaps you can adapt this for your setup.
You need to have your system point the url to the dnn installation.
On my setup, I go into Control Panel, Administrative Tools, Internet Information Services, websites, default website, right click this and select new virtual website, click next
enter an alias ie: mynewportal
click on browse and select the location of your DNN installation files
click next, set the permissions you require
click next to complete the wizard
All you need to do now is type in
http://localhost/mynewportaland your DNN installation will pick up that URL (as long as this is the URL you specified for the Parent Portal)