Antivirus program??

I got a free copy of PcCillen by Trend Micro on a mothorboard driver disc. Its been updated every week and never given any problems. I repair systems on the side as a hobby and have removed virus and cleaned drives with my system many times. PcCillin and Spybot search and destroy and regcleaner to get rid of things that are hard to uninstall or clear off your system. I'm cheap and free is good but only if the quality of the program is there and these are top notch. I hate Norton,and many of the systems I repair have at least a version of Norton antivirus on them,usually out of date and wont uninstall. If the whole utility package is installed I call it fully corrupted.