Visa Internet Security 2010 Highjacked

I apparently got a virus on my laptop. As soon as the internet connection is established, I keep receiving tons of messages informing me that my laptop is infected. A Visa Internet security 2010 window popups, where Firewall and Malware are off and it tells me that I have to buy a subscription to get rid of the problem. It apparently detects 28 trojan... programs. I ran Avast and another anti-virus program. They did detect some trojan programs but did not find the cause of the infection. When I try to go on Firefox, it says that Firefox is infected with Trojan_BNK.Win32.keylogger.gen