Malwarebytes & Spybot search & destroy are both useful tools in finding and removing issues but not antivirus solutions. Microsoft security Essentials, Avast or AVG will be more than enough for the average user so unless you do a lot of downloading from dubious sources you really don`t need any of the paid for solutions - Norton & Kaspersky in particular are really resource heavy and more of a hindrance in day to day use.