I would first try Trend Housecall (it's a free online check and is very good) - just Google it and follow the instructions -NO you do NOT want to buy it!
Once that's done look for AVAST! (again it's free and VERY good) on Google and download it, run it and use it as your main AV.
I have heard good things about AVG - but you can only run AVG or AVAST! - not both at the same time.
Good luck!
Ditto. Norton slows down your entire system and is very intrusive.
I dumped Norton and got Kaspersky long ago..System is faster and runs smooth.