Windows Security Center keeps warning me there's no antivirus software installed in my computer. I was a little worried so I ran Symantec Security Check, and it didn't detect my antivirus either. My AVG is installed for sure, I ran it and it didn't find anything, but running Trend Micro online scan I found a trojan. Any ideas on why this could be happening and if I should be alarmed? Never had any problems with AVG in 2 years I've been using it.