Are you trying to say that your non www. points to your www. alias and you don't want it to? If so, that's probably a simple fix (although I'm not quite sure why you would want a non www. not to point to your www. since it's quite valuable if not almost manditory to get good seo on the site). If you do want to eliminate the offending portal alias, you can log in as admin, go to the site settings page, scroll to the bottom and delete the portal alias with the www.
Depending on how your install is set up you may also have an issue with your host headers that needs to be resolved as well, but I'm not terribly qualified to point you in the right direction there.