yeah a cracked security program is sort of an oxymoron.
i've used nod32, avg, avast, antivir, norton, and clamwin.
I like avg the best because it's detection is good enough once updated, 99% of the time you get a virus you get the one thats popular at any given time. Its really nice how customizable AVG is, you can disable everything in it and use it as an on demand scanner so windows is running like a brand new fresh install, where other av programs after disabling the services & removing from startup still eat up some ram, you can use avg differently which is a nice option.
All the other av's I listed except clamwin are heavier duty IMO and better at trojans but thats why I use on demand scans with avg antispyware and a squared free, two good anti-spyware & anti-trojan scanners. One scanner will not keep you safe so whatever scanner you choose, be sure to have something behind it for trojans and spyware, AV programs not good for those. Still AVG is good, installed it on my friends pc & once it updated the real time protection found viruses without a scan, it works and is easy to use & light on resources.