Trojan found when installing Lexmark on an ME machine

Hi all,
I am working on a friends computer and he has ME, I have been trying to install his new Lexmark printer and AVG gives me a message saying that a trojan was found, I tried downloading a free copy of the driver with teh same results. I uninstalled AVG, installed Lexmark, then reinstalled AVG. all worked, then I ran a virus check and it found the trojan again, I deleted it, and printer seemed to work fine and I sent it home with him. But now it is back because he has been constantly been receiving errors since and they all reference Lexmark. Does anyone know what the problem could be?