Norton WMI.
The Security Center in Windows XP SP2 provides a feature to check the status of the antivirus in realtime but this wasnt effective because the antivirus provider didnt update thier products to take advantage of the Windows Security Center. Hence a user would see an alert whenever he switched on his computer warning that the antivirus wasnt upto date.
Today I saw that Norton had updated their products with the Norton WMI (Windows Management Instrumentation) update. Now Windows Security Center will be able to report the current status of the antivirus whether it is upto date or not. Read more about this at http://www.symantec.com/techsupp/sp2/faq.html