Making XP SP2's Security Center Recognize AV Software
It's rare to find a software package (one of the ones that power users recommend, anyway) that XP SP2's Security Center will recognize. So, to tell it that there actually is an AV program installed, go to the Control Panel and open "Security Center".
Under the "Virus Protection" header, Click the "Recommendations" button. Check the box in the window that pops up that says "I have an antivirus program that I'll monitor myself".
Hit "OK" and close the Security Center. You shouldn't be bothered by the Security Center anymore about AV protection