As uponthis mentoned, there's absolutly no reason why you should download (pirated)antivirus software from a p2p network when there's good FREE antivirus software, and apart from that If you wanted to plant a trojan or keylogger on someones box, where would you hide it in ?
I would choose no CD cracks for popular games or antivirus cracks as a way to infect other computers.
Just give
avast a try