Nod32 by Eset. dont know what it costs, but I know they have a free trial version(and I also know theres a crack to make it not a trial version). its the best one you can get. used to have problems gtting "infected" using norton and macaffee, but none since I switched. ( a little birdy told me its what the guys who make securty software for some of our governments most secure agencies use on thier personal computers, so if they trust it....)