I changed my preferred domain name from Google Webmaster Account. More problems, more headaches. I did it almost 3 weeks ago , and google did not updates their SERPs. Also google crawl now very hard my websites, and also ... it's not updating my old website (without www) ++++ i can't see logs because i am www.softgroups.com ,and not softgroups.com in google webmasters, so i can't see my top keyword queries,etc. ... Set preferred domain www.softgroups.com The preferred domain name www.softgroups.com was set on Nov 1, 2008. Note: Once you specify your preference here, it may take some time for changes to be reflected in our index. While Google doesn't guarantee that we'll show your URLs in the form that you prefer, we will use your choice as a suggestion to improve our indexing. To clear this association, click the "Clear this preference" button below. Help Code (markup):
you set that thing on 1st November and its 11 November today how can u say its three week now.... :~| any way you may have some backlinks with this non www version try to locate them via gogole webmaster tool (external link section), edit them and see the change. Check you site navigation too. may be you link to your home page from one of your internal page with this non www version.
Use the .htaccess to redirect all the www urls to non www urls. All your pages indexed in google will get changed upon next crawl (may take two ~ three crawls). The code of your .htaccess file will be EDIT: BTW You want www OR no www ??
add the 301 redirect as xxdomain told to u and hope ur site will get delisted in google next crawler bcoz its only page, if there are too many pages google takes quiet long long long time to remove them.
The best practice is to redirect your URL's to required one using L301 redirections as 'xxdomainxx' said. And search engines will follow the redirects then