I have AVG installed, but I recently found that this machine in the office was infected with a virus (Funny UST Scandal.avi.exe). q1. How can this machine be infected while an anti-virus software (AVG) is installed? q2. I'm suspecting that this occurred because a pen drive, that was known to carry a bunch of viruses, was stuck to this computer quite a few times. But ... I still don't quite understand how the infection took place. How did this happen ...???