??? i really don´t understand windows, im really starting to hate it. So one day the windows Security alert tell that my avast home free edition is not actualized, so start the avast! 4.7 antivirus and click on the thunder icon to update it, well it start and finished quickly… there is no such update, i don´t understand so the icon of the windows security alert is always active, what i have to do? i reinstall the antivirus and it´s the same… ??? ??? :-[
I, on the other hand, uninstalled the Security Center 
;D
http://forum.avast.com/index.php?topic=23457.msg193534#msg193534
Other answers for XP Security Center not detecting antivirus or firewall program could be found here: http://support.microsoft.com/kb/883792.