My son had something like this on his computer recently. Some security type icons appeared on his desktop and some windows kept on popping up saying his computer was at risk. I know those were rogues because I would identify all the AV/Spyware stuff I had installed - Norton, Adware and Spybot. However on the advice of my brother in law I had recently started switching over to AVG anti virus/protection. This identified and removed all the junk on my son's computer and it is now fine. When all the Norton subscriptions in the house are up, we will be an AVG shop.