There are differences between anti viruses!

The one you pay for are usually the ones that have viruses made for them to take it down. So using free ware thats NOT a resource hog is is the way to go.. I strongly recommend Avast. I have yet to get a virus from it. Its always stopped them before infecting my computer.. well my windows computer anyways.. No viruses for my linux computer, so loads of save downloading for me, WOOT!