I've used AVG products for a few years now and recently bought it directly from there site (cheaper here at Amazon) anyway its one of the best anti-virus softwares out there. It has stopped every trojan, virus, keylogger and such that I've come in contact with.
Although its a little heavy on system resources I didn't dock it a star for that, I've docked it a star for the new interface. I like the old one much better. Yeah I know it doesn't effect the software anyway if you need a good security system for your computer this would be a good choice for you. Works well with vista, windows 7 32&64 bit operating systems.
Would recommend especially over Norton or McAfee.