Trojan advice

I don't really know much about computers, and I've been lucky so far that I have not had much infect my laptop except cookies and one or two viruses that were detected and removed quickly. However I have a trojan on now, and it's apparently one that attacks the anti-virus itself, and I've heard those are hard to get rid of. I'm not sure what is the best thing to do. My AVG has detected it and quarrantined it, a scan of AVG afterwards revealed nothing and I have run other spyware/antivirus scans which haven't turned up anything either, but I wonder if there is more that I need to do or could do.