Personally I would avoid it like the plague, it slows most PC's significantly,is a real pain to remove completely and is expensive.
i stopped using it in 2004 when my PC was doing strange things , after uninstalling the (paid for) Norton software and using (free) Avast antivrius 7 viruses were found.
I would recommend Avast from Alwil software fre for personal use or you can purchase the professional edition I have used it for 3 years with no problems.
download here
http://www.avast.com/
If you want other better Antiviruses there are AVG,Mcafee,bitdefender,NOD 32, and PC cillin
Most aren't free just Avast and AVG go with Avast you'll like it