To know if the Anti Virus is active in your computer, go to services. Go to start and in run command type services.msc, you will see the services window. In that check the service corresponding to your anti virus software. I use CA antivirus and my CA related service is up and running (it is in automatic state) and is started. If you find your anti virus service is not started, you will need to start it and then make it automatic (double click and change the property to be automatic and NOT manual or disabled)