Antivirus program??

Actually this is the first computer i've had that doesn't have problems w/ Norton. I've had 5 new home computers and around 10 new ones at work, and everyone that I've had Norton on before had something that wouldn't run because of norton. There are times that I have to disable it to up or download something, but for now it's working quite well. I have enough memory that hogging a little bit isn't a problem, yet.