I recommend you go with Trend Micro. I personally think it is the best out there. I have been using it for years now and I haven't met any complications or errors. It doesn't slow down my computer too so you must give it a try. And by the way,
Trend Micro coupons is offering 10% off on their Antivirus plus AntiSpyware 2010 software so you might want to check that out.