Blueyonder PC Guard is free if you are on the 4meg and above packages (can't remember their names) I recently took Norton Anti-Virus and firewall off my system. I agree with Tycho AVG is working fine on my system.
I am also with blueyonder but there have been mixed reviews. I do know that it is uses more resources than Avg. It is also more than just anti-virus. Has firewall etc also.
If you can have it for free give it a go. You can always remove it if you don't like it.