hmm it would appear that Desktop Defender 2010 is malware, hmmm you should look into the Services to see If the Security Center Service would happen to be disabled.
In order to do that you would have to type :
services.msc in the start menu
Afterwards look for the "Security Center" service in the list, once you find out right click on it then click on "Properties", then look to see If the service may have either been stopped or disabled, If so then change the setting to Automatic, then click on "Start" in order to start the service back up again.
Hope this helps, report back with updated info !