Antivirus & Security Center

I have a 1 month old Dell Inspiron 1520, it came with Mcafee preinstalled, which ran out of trial days so I uninstalled it and then ran the Mcafee removal tool to delete any left over bits and pieces.

I purchased Norton Internet Security 2008 (always been a Norton fan) from PC World and installed that onto the laptop. The security center then says that I have no antivirus software installed, and despite Norton firewall being active - windows uses its own firewall because it does not detect another.

I cannot understand this because on the other vista computer the security center just detectes Norton, I have looked around online and have found out that the problem involves the Repository in the Wbem folder, I have tried various suggestions like on the following website;

http://www.pcreview.co.uk/forums/thread-3285051-2.php 

This is extremely thrustrating because everytime I load up my pc the security center displays this warning. Even if I set the security center to not monitor antivirus software - I still get alerts from the Norton Software telling me to enable the security center etc - again annoying!

Someone please help me!